Understanding the human footprint on the hydrological cycle/processes in a changing world

Human impacts on the water cycle are ever increasing. Some of our actions affect purposefully water stores and fluxes, while other human activities have unintended impacts on catchment. In the Anthropocene, humans have reshaped the water cycle and altered hydrological processes in three connected ways: (1) every agricultural, industrial, and domestic activity uses water directly and indirectly, (2) humans have directly modified 77% of the Earth's land surface, excluding Antarctica, through activities such as agriculture, deforestation, and wetland destruction, and (3) climate change is altering nearly every water store and flux (shrinking glaciers, permafrost melting, depleted groundwater, precipitation timing and intensity, drought, flooding, evapotranspiration etc.). These human modifications are creating a ‘water crisis’ not only by modifying water quantity (i.e. availability) dynamics but also water quality (i.e. pollution). In response to this crisis, we call on researchers to more explicitly conceptualise, quantify and understand the human footprint on the hydrological cycle/ processes, and implications for the sustainable management of freshwaters. In addition, nine years after the ‘Testing simulation and forecasting models in non-stationary conditions’ workshop at the 2013 IAHS general assembly, we urge researchers to present their most recent advances on preparing hydrological models to face a changing future. Recent advances on model robustness, associated testing, multi-modelling, understanding and reducing uncertainties are welcome. All spatial and temporal scales are concerned, as well as highly modified to pristine catchment (engineered, urban, rural and near-natural).

Convener: David Hannah | Co-Conveners: Gil Mahé, Guillaume Thirel, Honeyeh Iravani, Anil Mishra
| Fri, 03 Jun, 10:30–18:00|Room Rondelet 2
| Attendance Fri, 03 Jun, 15:00–16:30|Poster area

Orals: Fri, 03 Jun | Room Rondelet 2

Chairpersons: David Hannah, Gil Mahé, Anil Mishra
Taikan Oki, Naota Hanasaki, Hyungjun Kim, Qiang Guo, and Daisuke Tokuda

It is well known that various human activities are locally changing the hydrological cycles on the Earth. Climate change due to anthropogenic changes in atmospheric composition caused by greenhouse gas and aerosol emissions is altering the water cycle, including precipitation, evapotranspiration, runoff, groundwater infiltration, water temperature, and water quality. However, apart from such climate change impacts, are the changes in the hydrological cycle due to human activities basically local, and are the global impacts limited to climate change?

Irrigation not only uses river flows and groundwater, but also lowers surface temperatures to the extent that it must be considered in global climate change assessments, increasing evapotranspiration unnecessarily, especially in arid regions, and creating areas where evapotranspiration is greater than precipitation over continents that use upstream river runoff and fossil ground water for irrigation. This negative runoff is not only detectable in data from dense river flow observation networks, but is also suggested by the net divergence of water vapor in the atmosphere. These effects have also been observed and estimated from changes in total terrestrial water storage using gravity observations.

In recent years, human activities such as dam water storage and irrigation have been incorporated into so-called earth system models, which predict future climate change based on socioeconomic scenarios. As the local applicability of such global models is improving, there is an urgent need to further develop numerical models that can adequately represent both natural and human systems, and to interactively incorporate limiting factors such as water hazards and water supply and demand when constructing future projections of socioeconomic scenarios.

How to cite: Oki, T., Hanasaki, N., Kim, H., Guo, Q., and Tokuda, D.: Human footprint on the global hydrological cycles, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-81, 2022.

Tesfaye Belay Senbeta, Krzysztof Kochanek, Emilia Karamuz, and Renata Julita Romanowicz

One of the main driving forces - human factors - directly affects runoff processes by influencing the amount of water available and the development of hydrological droughts.The study investigated the role of human factors in the development of hydrological droughts in the Kamienna catchment and attempts to identify the main human factors that caused these changes through the analysis of remote sensing data. The hydro-climatic variables are divided into a baseline period and a disturbed period, using the method to detect changes in the runoff processes. We applied the rainfall-runoff model - SWAT - calibrated during the baseline period and used it to reconstruct the naturalized runoff during the disturbed period. The baseflow filtering algorithm was applied to separate baseflow from direct runoff. Drought indices: Streamflow Drought Index (SDI) and the Standardized Baseflow Index (SBFI) were used as indicators for hydrological drought analysis using observed and naturalized hydrological variables. The observation-based runoff indicators showed more successive hydrological droughts of longer duration and intensity in the catchment than the naturalization-based runoff indicators, especially in the 1980s, 1990s and 2000s. From 2010, shortly after the Wiory reservoir became operational, naturalized runoff matched observed runoff, indicating increased groundwater recharge and baseflow and⁄or systematic release of excess water from the reservoir during the dry season. This indicates the positive role of reservoirs on downstream runoff by mitigating hydrological drought events. Analyses of changes in land cover dynamics supported these changes caused by human factors in the watershed. This study contributes to our understanding of how human factors influence hydrological drought in the catchment, which is important for drought adaptation. 

Keywords: Rain-runoff model, hydrological drought, drought indices, land cover dynamics, human factors.

How to cite: Senbeta, T. B., Kochanek, K., Karamuz, E., and Romanowicz, R. J.: Rainfall-runoff modelling approaches for investigating the role of human factors in influencing hydrological drought, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-82, 2022.

Jean-Louis Perrin, Aïssatou Ghislaine Koné, Luc Séguis, Marthe Yéo-Soro, Chrystelle Montigny, and Droh Lanciné Goné

African cities have little or no sanitation or rainwater drainage network. The runoff draining diffuse pollution, combined with domestic and industrial wastewater is discharged directly into the receiving environment without treatment. In the Abidjan district, the densest neighborhoods in the Abobo municipality, are drained by the Djibi River. Contaminants transported during floods present an environmental risk, particularly for the Aghien Lagoon which receives the river. This lagoon, the largest freshwater waterbody near Abidjan, has been identified as a potential resource for the production of drinking water to face the tremendous difficulties in water supply of the city.

Urban wet weather discharges are made up of all the water discharged from urban zones and their drainage systems during and a few hours after a rainy event. The origin of the pollutants contained in these urban discharges is varied: atmospheric pollution, leaching of dry weather deposits accumulated in the basin, erosion and resuspension of the pollutants present in the sanitation and drainage systems.

To better understand and quantify pollutant transfers from the urban zones to the Aghien Lagoon, 8 representative floods were sampled (12 samples for each flood) in the Djibi River at 3 sites (2 sites downstream from urban zones, 1 site just upstream from the Lagoon) between 2019 and 2021. Physico-chemical parameters and suspended solid, nutrient, dissolved and total trace element concentrations as well as discharge were measured to evaluate their environmental impact on the Aghien Lagoon.

During floods, concentrations of pollutants increased systematically, reaching very high values. The concentration peaks were observed at the rising limb of the flood, before the peak of discharge, for the majority of the analyzed elements. We also observed a massive remobilization of pollutants from storage areas. The most obvious is located in urban zones. In addition of the clean-up of urban areas, we also observed a remobilization of the pollutants accumulated, during low flow conditions, in the river bed itself.

The pollutant loads transferred to the Aghien Lagoon are very important and contribute significantly to the reduction of its water quality which could increase the treatment cost of a pumping under construction.


How to cite: Perrin, J.-L., Koné, A. G., Séguis, L., Yéo-Soro, M., Montigny, C., and Goné, D. L.: Urban wet weather discharges and pollutant dynamic in the Djibi River (Abidjan – Côte d’Ivoire), IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-39, 2022.

Irene Palazzoli, Alberto Montanari, and Serena Ceola

Surface water sustains freshwater ecosystems by preserving the integrity of their habitats and supplies water to many anthropogenic sectors. However, human activities impact surface water bodies and determine a progressive reduction of their extent. In particular, the process of urbanization due to urban population growth is expected to produce an increase of the exploitation of surface water in the surroundings of cities.

Here, we examine the driving role of urban areas in the spatial distribution of surface water loss across river basins of the contiguous United States (CONUS) using remote sensing data. We define surface water loss as any conversion from surface water to land that occurred between 1984 and 2018 and we compute the frequency of these losses as a function of distance from urban areas. We find that in all the rivers basins of the CONUS surface water loss is more intense around cities and declines as the distance from human settlements increases. Therefore, we define a distance-decay model that follows a truncated exponential probability distribution which is able to reproduce the observed decreasing trend, proving that urban areas cause an increasing stress on surface water resources in the proximity of human settlements. Moreover, we observe that the decrease in surface water loss is faster in river basins with larger urban agglomerations, indicating that the influence of urban areas on the spatial distribution of surface water loss increases as the extent of urban areas increases as well.

Finally, we investigate the role played by climate in the spatial interaction between urban areas and surface water losses and we notice that different pattern of exponential decay of surface water loss are found across the main climatic regions of the CONUS. Specifically, in areas with temperate and continental climate the presence of urban areas determines local and concentrated surface water losses, while losses are more distributed and reach greater distances in arid regions.

How to cite: Palazzoli, I., Montanari, A., and Ceola, S.: Spatial Influence of Urban Areas on Surface Water Loss Across the Contiguous United States, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-7, 2022.

Valentin Brice Ebodé, Gil Mahé, Jean-jacques Braun, Jean-guy Dzana, Jules Remy Ndam Ngoupayou, and Bernadette Nka Nnomo

The objective of this study is to understand the impact of rainfall variability and anthropization on the flows of the Mefou watershed over a recent period. For this, the hydropluviometric data of the catchment concerned were analyzed using the Pettitt test. Likewise, the dynamics of the main land-use patterns have been assessed, using supervised classifications carried out from the processing of Landsat satellite images of the basin studied at two dates. The results of this study show that the average and extreme flows of this basin have been increased since 1985-86, unlike the rainfall, which generally decreases for all seasons from the 1970s, apart from the summer, where the reverse is observed. Land-use changes (increase in impervious areas and a decrease in forest and water bodies) seem to be the main cause of the observed increase in runoff. The rainfall changes observed in this basin have just contributed to amplifying this increase in runoff in some cases and attenuating it in others. The summer and the spring for which the rainfall recorded respectively an increasing break and no break are also the seasons for which the increases in runoff are the most important. Conversely, autumn and winter, which saw significant decreases in rainfall, experienced the smallest increases. These results could be useful for long-term planning of water demand and use in this basin, as well as for improving future simulations of main collector flow and preventing socio-environmental disasters like flooding.

Keywords: Mefou, variability, precipitation, runoff, land use patterns

How to cite: Ebodé, V. B., Mahé, G., Braun, J., Dzana, J., Ndam Ngoupayou, J. R., and Nka Nnomo, B.: Flows variability in a forest watershed undergoing accelerated urbanization: the case of Mefou (South Cameroon), IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-86, 2022.

Mohamed Saadi, Ludovic Oudin, and Pierre Ribstein

Urbanization changes the rainfall-runoff relationship mainly by increasing catchment imperviousness. This increase questions the importance of antecedent soil moisture in runoff generation in urbanized catchments, which are composed of a mix of rural and urban surfaces. Using a large sample of 70,227 events in 852 United States catchments, we quantified the relative importance of total impervious area (TIA) and antecedent soil moisture (ASM) in determining the runoff ratio (RR) at the event scale. To this end, we grouped the events into 30 classes of TIA and 30 classes of ASM, and we applied linear regression models to analyze the evolution of RR depending on TIA or ASM. The key findings are as follows: (1) Compared to event characteristics (precipitation amount and intensity), ASM showed a stronger ability in predicting the event-scale RR. (2) Even in catchments with high TIA, ASM still played an important role in runoff generation. (3) The impact of urbanization on the relationship between RR and ASM was relatively gradual, but became significant as TIA exceeded 5%. These empirical results are beneficial for advancing the process-based representation of the rainfall–runoff relationship at the scale of an urbanized catchment. They are potentially useful to revise the widely applied methods in practical urban hydrology by elucidating the interplay of ASM and TIA in influencing the catchment response.

How to cite: Saadi, M., Oudin, L., and Ribstein, P.: How does the relationship between soil moisture and runoff evolve with increasing urbanization?, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-172, 2022.

Lunch break / Exhibition for the public
Chairpersons: Gil Mahé, David Hannah, Honeyeh Iravani
Kate Heal, Amira Elayouty, Susan Waldron, E. Marian Scott, and Amy Pickard

Wind farms can help to mitigate increasing atmospheric carbon (C) emissions. However, disturbance caused by wind farm development must not have lasting deleterious impacts on landscape C sequestration. To understand the effects of wind farms on peatlands, we monitored streamwater in five catchments (5.7–31 km2area) draining Europe’s second largest onshore wind farm at Whitelee, Scotland, UK for 10 years after wind farm development that occurred in phases. Dissolved organic carbon (DOC) concentrations were measured every 2–4 weeks and DOC fluxes estimated using flow from either direct measurements in the catchments or scaled via catchment area from a nearby river flow gauge. Similar measurements were made at a nearby peatland catchment unimpacted by wind farm development that acted as the best possible reference site. Generalised additive mixed models (GAMM) were fitted to all catchments to assess differences in trends and seasonality in DOC and flow between catchments. Interactions terms allowed for the possibility of changing seasonal patterns, and temporal correlations were included in the models and formal testing using an AR(1) structure. Change points in DOC trends were identified using first derivatives of the estimated trends and compared with the timings of wind farm construction. DOC exports from the wind farm-impacted catchments are high at 17–34 g C m-2 year-1. The models showed increasing trends in streamwater DOC concentrations and fluxes in the wind farm-impacted catchments, with timing apparently synchronous with the development phases. In contrast, streamflows were more stable. Trends and seasonality of DOC concentrations and fluxes were different in the reference catchment during the study period. Hydrological and biogeochemical processes driving the DOC response of peatland catchments to wind farm development will be discussed, and their consequences for landscape C sequestration assessed.

How to cite: Heal, K., Elayouty, A., Waldron, S., Scott, E. M., and Pickard, A.: Untangling land use and climate impacts on catchment water quality: Decadal trends in catchment dissolved organic carbon export in response to wind farm development on peatland, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-127, 2022.

Thibault Lemaitre-Basset, Ludovic Oudin, Guillaume Thirel, and Lila Collet

Air temperature increase due to climate change can lead to an increase in evapotranspiration, depending on whether the atmospheric demand is water or energy limited. This results in the intensification of the transfer from the continental hydrological compartment to the atmosphere. Investigating the uncertainties in the representation of potential evapotranspiration (PE) can provide a better understanding of the sensitivity of hydrological projections to atmospheric demand. This work summarizes our findings on different aspects about PE evolution under climate change and the uncertainties associated. First, we explored the relative importance of the contribution of PE formulations to the total uncertainty in PE projections, compared to the other steps in the modeling chain. Second, we evaluated the importance of the negative feedback of atmospheric CO2 concentration on evapotranspiration for hydrological projections by modifying the stomatal resistance equation in the Penman-Monteith equation according to three formulations proposed in the literature to evaluate the sensitivity of hydrological projections to vegetation responses.

Regarding the importance of PE formulations on PE projections, it appears that the relative role of formulations is minor compared to other sources of uncertainty (namely climate models and greenhouse gases emission scenarios). Regarding the impact of CO2, results highlight a zone of uncertain change from decreasing to increasing average annual runoff, depending on the emission scenario and stomatal resistance equation. Thus, in the north of France, where PE fluxes are energy-limited, various levels of runoff response are showed with three tested formulations. The use of a PE formulation with stomatal resistance as a function of atmospheric CO2 could be used as forcing of a conceptual hydrological model, to include vegetation responses.

How to cite: Lemaitre-Basset, T., Oudin, L., Thirel, G., and Collet, L.: Understanding uncertainties in future evapotranspiration projections to study the impact of climate change on hydrology over France., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-199, 2022.

Natural and anthropogenic changes of inundation conditions of highly populated floodplains in Russia
Inna Krylenko, Vitaly Belikov, Andrey Kalugin, Aleksey Sazonov, and Elena Zakharova
Alena Bartosova, Berit Arheimer, Alban de Lavenne, René Capell, and Johan Strömqvist

Continental and global dynamic hydrological models have emerged recently as tools for e.g. flood forecasting, large-scale climate impact analyses, and estimation of time-dynamic water fluxes into sea basins. One such tool is a dynamic process-based rainfall-runoff and water quality model, Hydrological Predictions for Environment (HYPE, see https://hypeweb.smhi.se/). We present and compare historical simulations of runoff, soil moisture, aridity, and sediment concentrations for three nested model domains using global (WWH), continental (Europe, E-HYPE), and national (Sweden, S-HYPE) catchment-based HYPE applications (Table 1). Future impacts on hydrological variables from changing climate were then assessed using the global and continental HYPE applications with ensembles based on three Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs). The comparison was carried out for ensemble averages as well as for individual GCMs to illustrate the variability and the need for robust assessments.

We illustrate how modeling across nested domains enables additional assessments of robustness in terms of projected impacts, modelling setups, and model performance criteria. After accounting for the spatial resolution, simulated historical runoff values were quite similar among the nested models while sediment concentrations varied considerably in spatial patterns. Regardless of the variation, the global model was able to provide information on climate change impacts comparable to those from the continental and national models for hydrological indicators.

Global hydrological models are shown to be valuable tools for e.g. first screenings of climate change effects and detection of spatial patterns and can be useful to provide information on current and future hydrological states at various domains. The challenges are (1) in deciding when we should use the large-scale models and (2) in interpreting the results, considering the uncertainty of the model results and quality of data especially at the global scale. Comparison across nested domains demonstrates the significance of scale and model performance and supports the need to use model ensembles for large-scale analyses instead of a single model.

Bartosova et al, 2021. Large-Scale Hydrological and Sediment Modeling in Nested Domains under Current and Changing Climate. Journal of Hydrologic Engineering 26, 05021009. https://doi.org/10.1061/(ASCE)HE.1943-5584.0002078 

How to cite: Bartosova, A., Arheimer, B., de Lavenne, A., Capell, R., and Strömqvist, J.: Assessing robustness of large-scale hydrological and sediment modeling using nested domains under current and changing climate, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-155, 2022.

Ali Hadour, Gil Mahe, and Mohamed Meddi

This work focuses on the contribution of the documentation of the fluvial sedimentary archive in the study of the contribution of rainfall and large dams in the decline of sedimentary inputs of the Cheliff Wadi at the outlet. Therefore, three sediment cores, taken in the lower Cheliff valley, were studied through the paleohydrological approach. Such an examination aims, on the one hand, to establish a chronology of depositional accumulation and, on the other hand, to evaluate the ability of the information incorporated in the sedimentary archive to transcribe the evolution of the hydrosedimentary signal and the fluctuations of the controlling factors.

The results reveal: a strong variation in the granulometric distribution of the deposits and a progressive decline in the progressive decline in the rate of sediment accumulation. Thus, the upper part of the core is mainly made of particles belonging to the fine granulometric class that have accumulated with fine that accumulated with an average rate of about 1.31 cm / year. Contrary to the deposits composed of a succession of coarse and fine sedimentary layers, and showing a rhythm of accumulation much more superior, whose value is evaluated to 16 cm/year. However, the fluctuations observed in the granulometric composition and the accumulation rate of the deposits correlated strongly with the evolution of the rainfall signal and/or the multiplication of the number of large dams. Indeed, relatively coarse deposits and a higher accumulation rate correspond to the wet period before 1980.  Then, the decrease in rainfall was accompanied by a longer accumulation rate and deposits composed mainly of fine particles. In addition, the recently built dams, bringing the outlet of the watershed closer and closer, have a drastic effect on the deposition process.

Key words: Sedimentary archive, paleohydrological approach, Cheliff, rainfall, granulometric profile.

How to cite: Hadour, A., Mahe, G., and Meddi, M.: Reconstruction of the evolution of the hydro-sedimentary signal to the sea from the study from the study of the sedimentary archive: Case of the Cheliff wadi, Algeria., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-430, 2022.

Luc Descroix, Sylvie Paméla Manga, Safietou Soumaré, El Hadj Kourahoye Diallo, Fatoumata Binta Diallo, Mamadou Sow, Yaya Sakho, Ababacar Fall, and Amadou Hamath Dia

Le Fouta Djallon est considéré comme le « château d’eau » de l’Afrique de l’Ouest. La plupart des grands cours d’eau d’Afrique de l’Ouest y prennent leur source. Les eaux provenant de ce massif constituent l’essentiel du débit des grands cours d’eau apportant de l’eau douce à la bande sahélo-soudanienne, en particulier, d’ouest en est, la Gambie, le Sénégal et le Niger.

Ces hauts plateaux sont aussi une région très peuplée, et ce depuis plusieurs siècles, ayant été un foyer culturel et religieux en lien avec les grands royaumes peuls qui ont dominé la sous-région jusqu’à l’arrivée des colons européens au 19ème siècle.

De ce fait, les zones rurales (l’essentiel du paysage) de la partie la plus haute du massif, la plus haute et la plus densément occupée, est caractérisée par un paysage construit, très végétalisé malgré l’absence quasi-totale de forêts primaires. Les haies, les bosquets, les forêts galeries, les forêts secondaires, les arbres nombreux autour des concessions, en bordure des routes, autour et dans les champs, constituent une partie riche et dynamique de l’agrosystème, avec des activités très variées de polyculture/élevage et foresterie. 

Une des formes les plus construites et intenses de paysage agraire typique de ce château d’eau est la « tapade » un jardin de case très intensif et fermé, protégé du bétail par des haies de pierres renforcées de haies vives, et caractérisée par un étagement des espèces cultivées, des racines (manioc, igname, arachides et, de plus en plus, pommes de terre) aux arbres fruitiers (papayers, manguiers, agrumes, etc) en passant par des arbustes utiles tels que le caféier.

Ces activités intensives pratiquées sur des sols construits très riches en matière organique et de structure aérée, ont des rendements élevés et une très forte perméabilité et capacité de rétention en eau, ce qui constitue sans conteste un apport des habitants de ce massif à la pérennisation du château d’eau en tant que tel !


How to cite: Descroix, L., Manga, S. P., Soumaré, S., Diallo, E. H. K., Diallo, F. B., Sow, M., Sakho, Y., Fall, A., and Dia, A. H.: Le rôle hydrologique de l’intensification de l’agriculture dans le Fouta Djalon, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-591, 2022.

Chairpersons: David Hannah, Guillaume Thirel, Honeyeh Iravani
Thomas Recknagel, Valery Vuglinsky, and Claudius Fleischer

Reservoirs have a great influence on the flow regime of rivers. Time series of dam management can help to quantify this influence and attribute the causes of flow regime changes. Often, records of dam management in the 20th century are scattered across many different locations and are not available in digitized form. Using the example of the Bleilochtalsperre, the largest reservoir in Germany, we show how the digitization of handwritten records can be done efficiently by using contemporary tools and which conventions for data formats and metadata formats can be used. The practical example is intended to serve as a blueprint to support initiatives that increase the dataset of the International Data Centre on Hydrology of Lakes and Reservoirs (HYDROLARE), which is a WMO data center within the Global Terrestrial Network - Hydrology (GTN-H).

How to cite: Recknagel, T., Vuglinsky, V., and Fleischer, C.: Data rescue of reservoir management data on the example of Bleiloch Reservoir, Germany, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-587, 2022.

Germano Ribeiro Neto, Paolo Colombo, Louise Cavalcante, Sarra Kchouk, Lieke Melsen, Alexandre Cunha Costa, David W. Walker, Eduardo Martins, and Pieter van Oel

The rampant construction of reservoirs can cause a concentration of water in certain regions and scarcity in others. This gives rise to conflicts and social pressure to build more reservoirs, creating a vicious cycle. An example of this is Ceará, a  Brazilian state often affected by intense drought events. State-level water resources management is mainly focused on the administration of 155 public “strategic reservoirs”. There is also a Dense Network of (non-strategic) Reservoirs (DNR) formed by almost 107,000 dams that are informally constructed to unknown specifications, unmonitored, and their management is not aligned with the state and watershed level governance. The occurrence of a multi-year drought (2012-2020) revealed that a DNR can play a significant role in the evolution and intensification of drought events. We aimed to analyze this effect in the Banabuiu River basin from a socio-hydrological perspective. We modeled two scenarios through a mesoscale semi-distributed hydrological model for semi-arid regions (WASA): 1) simulating the current configuration of the hydrological system and 2) simulating a condition without the DNR. To explore the DNR effect on drought events, we used the novel Drought Cycle Analysis method (DCA) which combines the Standardized Precipitation Index (SPI) with the Volume Deficit information (VD, deviation of half of the total capacity of the monitored reservoirs). We also conducted interviews with smallholder farmers who are the main users of non-strategic reservoirs to understand the societal impact of these structures. Our results showed that the presence of the DNR advances the transition from meteorological towards hydrological drought and leads to slower recharge of the strategic reservoirs between and during drought events. On the other hand, farmers explained their water security has increased after having a non-strategic reservoir on their land. The interviews also revealed that non-strategic reservoirs are the primary water source for most farmers. Although there are other options for accessing water during multi-year drought events, these generally cannot meet the farmer's water demands, thus causing a reduction in their productive activity .

How to cite: Ribeiro Neto, G., Colombo, P., Cavalcante, L., Kchouk, S., Melsen, L., Cunha Costa, A., W. Walker, D., Martins, E., and van Oel, P.: The influence of a dense network of small reservoirs on drought evolution in a semiarid region  , IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-672, 2022.

Tommaso Pacetti, Jerome El Jeitany, and Enrica Caporali

Based on the integration of hydrological modelling and Water Footprint (WF) analysis, this study aims at developing a methodology to analyze both the supply and demand of Water related Ecosystem Services (WES) connected to the agricultural sector under climate changes scenarios. The WES demand by the agricultural sector is determined using the WF Assessment methodology estimating the green, blue, and gray WF component and their variability due to climate change. The WES supply is analyzed by applying the Soil Water Assessment Tool (SWAT). The model simulates the main hydrological processes thus allowing the spatial explicit quantification of the variables estimating the water availability in its three components. After calibration and validation, possible scenarios of changes in water availability are evaluated under 20 climate change scenarios by means of  12 indicators of Hydrologic alteration (IHA) being the most representative of the flow regimes in Europe. Finally green, blue, and gray WES Footprint (WESF) through dedicated indicators in order to identify the main hotspots in agriculture water management and their future projections. The methodology is applied to a specific case study in the upstream part of the Arno River basin (Central Italy). The analysis allows the spatial explicit identification of the main hotspots associated to agricultural production in future scenarios. All scenarios outlined hydrological parameters that alter flow regime and affect surrounding ecosystem, despite a discrepancy between the northern part and the southern part on the basin. Magnitude of variability in monthly water availability and the changes in WF are explored suggest possible challenges to address. The use of footprint indicators, and in particular of WESF, can lead to a more sustainable water management revealing hidden costs and impacts of production of goods and services and sustaining the formulation of a conscious and integrative basin management plan.

How to cite: Pacetti, T., El Jeitany, J., and Caporali, E.: Evaluating water Ecosystem Services Footprint of agricultural production under climate change scenarios, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-656, 2022.

Rodolfo Nobrega and Iain Colin Prentice

While land-cover clearing (LCC) immediately reduces evapotranspiration (ET), its effects on other water fluxes, such as river discharge and terrestrial water storage, exhibit contrasting responses depending on location and scale. One explanation for this is that LCC triggers a series of asynchronous disruptions in the equilibrium of hydrological processes that was established upon the long-term balance with regional climatological, edaphic, and geological characteristics. Water fluxes under these circumstances are not well represented by hydrological models that have Budyko-like approaches or rely on the stationarity of the hydrological responses. The complexity of such analysis is incremented once LCC is followed by the conversion to pastures and crops established over random spatial and temporal patterns throughout river basins. Here, we propose an analysis of river discharge and root zone storage capacity (RZSC) to unveil underlying relationships between stream dynamics and water consumption by plants. We use a time-series segmentation and residual trend analysis on streamflow and precipitation of high-order tributaries of the Tapajós River in the Amazon whose catchments underwent an intense land-use change over the past decades. We estimate the RZSC using the mass-curve balance method by considering the annual land-cover changes over a >30-year period. Despite the common belief that increases in river discharge are primarily caused by reduced ET when precipitation trends are not significant, we show that this might not be the main trigger of streamflow change in these major Amazon catchments. Instead, the reduction in the RZSC caused by changes in the water consumption by plants over the dry season is tightly associated with the increased baseflow contribution to rivers. Finally, we analysed gross primary productivity (GPP) and ET estimates generated by a model based on eco-evolutionary optimality that integrates the water and carbon cycles at the canopy level. We found that trends in ET from croplands are not as pronounced as trends in GPP. Although RZSC is quantified using the water deficit driven by ET, changes in RZSC are more correlated to changes in GPP. Our results highlight the importance of considering the carbon cycle in hydrological assessment studies.

How to cite: Nobrega, R. and Prentice, I. C.: Holistic analysis of the carbon and water cycles to quantify the human footprint in basin-wide hydrological processes in the Amazon, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-598, 2022.

Djigbo Félicien Badou, Yacouba Yira, and Jean Hounkpè

Water use planning is vital, making hydrological modelling crucial for the development of human society. This role of hydrological modelling is rendered even more prominent given current population growth and global warming resulting in more pressure on water resources. Nonetheless, most quantitative hydrological predictions remain fundamentally uncertain leading to uncertain water availability assessment. This is so, partly, because streamflow continues to be used as the main dependent variable, calibration and validation data length and content are arbitrarily selected, and water balance components taken individually are not quantified with the best prediction models. This paper discusses three ideas for stepping further away from uncertainty in quantitative hydrological predictions. Less uncertain hydrological predictions can be achieved through (i) blue water and green water-based hydrological models validation, (ii) blue water and green water-based multi-model evaluation of water resources, and (iii) a conditioned selection of calibration and validation data.

How to cite: Badou, D. F., Yira, Y., and Hounkpè, J.: Prediction in quantitative hydrological modelling: a small step away from uncertainty, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-456, 2022.

Flora Branger, Ivan Horner, Isabelle Braud, Hilary McMillan, and Claire Lauvernet

Hydrological signatures are indicators derived from observed or modelled hydrological data, that can be interpreted in terms of physical processes and linked to specific catchment response functions. They can be valuably used for the study of rainfall-runoff processes in a specific catchment, for catchment classification and comparison, or for hydrological model calibration and evaluation, in order to strengthen their ability to represent the dominant processes. Multiple signatures, using all kinds of hydrological variables (but mostly streamflow) are now available and reported in the litterature. However, the question of selecting and evaluating the signatures themselves has received less attention. How to build a set of signatures encompassing the various aspects of catchment response ? How to evaluate the information content and redundancy of these signatures ?

Our contribution presents a set of signatures based on commonly available hydrological variables (precipitation, streamflow and air temperature time series). It was built according the partitioning, storage and release catchment conceptual model of Wagener et al. (2007). It also includes the cryosphere compartment. Alongside already well-known signatures, new signatures were designed to fill gaps for the description of some catchment response functions. Two different methodologies were used to evaluate the signatures, based on the use additional variables provided by long-term hydrological observatories on the one side, and on a sensitivity analysis performed with a process-based hydrological model on the other side. The most relevant signatures could be identified and are available for further hydrological studies.

How to cite: Branger, F., Horner, I., Braud, I., McMillan, H., and Lauvernet, C.: Building and evaluating a set of hydrological signatures, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-722, 2022.

Posters: Fri, 3 Jun, 15:00–16:30 | Poster area

Andrey Kalugin and Sergey Lupakov

The main goal of this study is to obtain new results of a physical assessment of the modern hydrological consequences of the natural and anthropogenic components of climate change based on the synthesis of detailed process-based models of river runoff formation using the ECOMAG software and an ensemble of the Earth system models (ESMs) within the large river basins of Eastern Siberia. This approach allows calculating the river flow using the ESMs-based data over the observation period under two scenarios: (1) taking into account the anthropogenic impact of increasing greenhouse gas emissions and (2) taking into account only internal fluctuations of the climate system and natural external forcing.

In the first stage, the long-term annual and seasonal runoff of the Lena and Selenga rivers over the period of instrumental observations was evaluated using the ESMs-based data as boundary conditions in spatially distributed hydrological models. The ensemble of 4 ESMs (GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC5) satisfactorily reproduces annual and seasonal values of both air temperature and precipitation and river runoff calculated using hydrological models over the observation period. The PBIAS in the calculation of annual runoff was 4% and 5% for the Lena and Selenga rivers, respectively.

In the second stage, the attribution of natural and anthropogenic climate-driven runoff change over the historical period was evaluated by runoff formation models and ESMs, including before streamflow measurements on the Lena and Selenga rivers. According to the results of numerical experiments, it was found that the anthropogenic component of climate change in the dynamics of the Lena runoff is weak, i.e. during the observation period the Lena River flow statistically significantly increases, but it occurs mainly due to natural climate variability. The changes in the Selenga runoff are intensely influenced by the anthropogenic component of climate change. This has been particularly noted since the 1970s, when in the case of natural climatic conditions the flow would have increased, but taking into account anthropogenic greenhouse gas emissions, it has decreased especially since the mid-1980s due to a decrease in summer precipitation, which caused the last low-water period of 1996-2017 in the Selenga basin.

How to cite: Kalugin, A. and Lupakov, S.: Climate change attribution in the river runoff using model-based approach, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-252, 2022.

Yali Woyessa

Rapid population increase, industrialization and pollution are putting a strain on available and diminishing freshwater resources. Recent climate projections suggest a drop of up to 10% in precipitation in most of Southern Africa by 2050. The main aim of this paper is to model the impact of climate change on water resources in a semi-arid river basin in South Africa using two downscaling approaches: statistical downscaling (SDE) and dynamic downscaling (CORDEX) approaches. Both SDE and CORDEX data were derived from the GCM simulations of the Coupled Model Inter-comparison Project Phase-5 (CMIP5) and across two greenhouse gas emission scenarios known as Representative Concentration Pathways (RCP) 4.5 and 8.5 with a spatial resolution 25 km × 25 km for SDE and 50 km x 50 km for CORDEX. Six GCM models were used for SDE set of data and eight for CORDEX data. SWAT hydrological model was run using these data for a period of 2020 to 2050.

For SDE data, comparison of measured data with simulated historical data showed strong correlation (R2 ≥ 0.9), which is indicative of the reliability of projected future climate. Varied results were obtained depending on the type of climate model used, but generally, the trends were similar in most cases. However, the multimodel average showed a possible decrease in precipitation (by 14%), a decrease in water yield (by 15%) and an increase in potential evapotranspiration (by 10%). For CORDEX data, the result showed similar strong correlation (R2 ≥ 0.9). The multimodel average showed a possible decrease in precipitation (up to -3%), a decrease in water yield (up to -13%) and an increase in potential evapotranspiration (ET) (up to +22%). The latter is indicative of possible drought spells between rainy events. The SDE approach showed much more pronounced decrease of precipitation and water yield compared to the CORDEX approach. This difference could be attributed to the difference in spatial resolution of the two downscaling approaches. However, it is expected that the results of this study could assist in policy formulation to mitigate the negative impact of climate change in the region.

How to cite: Woyessa, Y.: Assessment of Climate Change Impact and Comparison of Downscaling Approaches: A Case Study in a Semi-arid River Basin, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-253, 2022.

Ilaria Clemenzi, Yiheng Du, and Pechlivanidis Ilias

Ongoing warming strongly influences the water cycle at the regional scale and increases concerns about future streamflow changes with consequences for water availability and potential intensification of hydrological extremes, i.e. floods and droughts. Detecting and identifying controlling factors of future streamflow changes is a key point to understand the hydrological response to changing climate and develop tailored strategies for the water resources management and risk adaption. In this study we investigate the streamflow changes, including extremes, across Europe in the mid (2041-2070) and late (2070-2099) century. We used streamflow simulations from the E-HYPE hydrological model and the EURO-CORDEX climate model projections. The sensitivity of streamflow changes to the climatic factors compared to the reference period (1981-2010) is evaluated with the climatic elasticity method based on the Budyko framework. Moreover, we assess the spatial consistency and uncertainty of the streamflow changes due to the ensemble variability. Results show that the sensitivity of streamflow changes to climatic change varies depending on the climatic gradient and physiographic properties of the domain.

How to cite: Clemenzi, I., Du, Y., and Ilias, P.: Attribution of streamflow changes to future climate projections across Europe, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-569, 2022.

Honeyeh Iravani and Julian R. Thompson

The hydrological characteristics of wetlands exert important ecological controls that influence the provision of many ecosystem services that wetlands provide. Wetlands are, however, subject to a host of pressures that include changes in their hydrology or the hydrology of the catchments in which they are located. Stressors include climate change, water withdrawals and diversions, as well as land-use change. Resulting alterations in wetland hydrological regime, which in some cases can occur relatively rapidly, outside the ecosystem's natural variability can have profound ecological consequences. Wetlands are, in particular, sensitive to changes in the quantity and timing of water inflows. This is especially true of floodplain and lacustrine wetlands located in the lower reaches of river systems. Assessment of the impacts of these changes and the development of strategies for sustainable wetland management, conservation, and restoration requires the application of numerical models that can accurately represent the hydrological conditions within wetlands and their catchments. High resolution, physically-based models provide a means of representing the often complex interactions between biophysical characteristics and hydrological processes. This study is based on the development of a MIKE SHE / MIKE 11 model of Zayanderud River Basin, which ultimately discharges into the Gavkhuni wetland, a brackish, shallow, lake and one of Iran's Ramsar sites. The wetland is the subject of local and national concern given the drought conditions that have persisted, with inflows from the Zayanderud River being eliminated in recent years. The MIKE SHE model employs a wide range of data obtained from national and global datasets whilst a number of approaches are used to address the significant gaps that characterize meteorological datasets for the river basin. The model also includes irrigation abstractions that are implicated in the decline of the Gavkhuni wetland. Following calibration/validation against observed river discharge at nine stations, the model is used to undertake a preliminary investigation of the impacts of climate change, with a particular emphasis on inflows to the Gavkhuni wetland, using an ensemble of GCMs.

How to cite: Iravani, H. and Thompson, J. R.: Simulation of the hydrological impacts of climate change on the Zayanderud River Basin and the implications for the Gavkhuni Ramsar wetland, Iran., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-285, 2022.

Alexis Jeantet, Julien Tournebize, Philippe Martin, and Guillaume Thirel

Subsurface drainage is a hydraulic technique currently used on agricultural soils showing strong waterlogging issues. This technique is applied on near 10% of French arable soils. Consequently, assessing its future in a context of climate change is relevant since subsurface drainage may have a major influence on the environment, specifically on agricultural water pollution. Here, the purpose is to analyse the evolution of hydrological indicators of subsurface drainage under climate change by 2100, on the La Jaillière plot being representative of French drainage in the Great West region. We define seventeen hydrological indicators to best describe the main aspects of subsurface drainage: drained water balance, temporality of the drainage season, flood events… These indicators are simulated by modelling subsurface drained discharge on the projected future using three hydrological subsurface drainage models: DRAINMOD, MACRO and SIDRA-RU. These three models are fed by twelve climate projections CPs provided by the EURO-CORDEX project, being selected by Météo-France to ensure the representativeness of future conditions in France. We consider three climatic scenarios RCPs (Representative Concentration Pathways): the RCP 2.6 (optimistic), the RCP 4.5 (intermediate) and the RCP 8.5 (pessimistic). The propagation of uncertainties on the hydrological indicators from the modelling chain is assessed by variance decomposition using the QUALYPSO method, from the various potential sources of uncertainties (hydrological models, CPs and RCPs).  Preliminary results obtained with the SIDRA-RU model alone showed that subsurface drainage will be exposed to more extreme events such as more intense flood events over shorter periods by 2100. Depending on RCPs, the sustainability of the current network may no longer be ensured.

How to cite: Jeantet, A., Tournebize, J., Martin, P., and Thirel, G.: Uncertainty propagation in the modelling chain of the impact of climate change on a specific site on French subsurface drainage, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-435, 2022.

G.-Fivos Sargentis, Ilias Taygetos Meletopoulos, Theano Iliopoulou, Panayiotis Dimitriadis, Efthimis Chardavellas, Dimitra Dimitrakopoulou, Aimilia Siganou, David Markantonis, Konstantina Moraiti, Konstantinos Kouros, Maria Nikolinakou, and Demetris Koutsoyiannis

In traditional and isolated societies human needs were limited and the resources were sufficient. For example, 70 years ago, water needs per capita in Greece were about 7,2 m3/year. But the basic perception of development is the abundance of water resources. For example, tourist development changes the culture of water consumption as modern way of living needs 150 m3/year per capita. In the same time one visitor would prefer accommodation with pools demanding even more fresh water.

Fortunately, there are many technological solutions to cover this gap of consumption. Unfortunately, some of them are not efficient or sustainable and other have big cost of energy.

This research examines the case study of the Municipality of Western Mani in South Greece, an area with high touristic development, detects the transformation of needs and potential technical solutions which are evaluated with criteria: needs coverage; sustainability; preservation of the landscape.

Stochastic models for the simulation of the function of water infrastructures in different scales (from traditional to modern) are applied.

How to cite: Sargentis, G.-F., Meletopoulos, I. T., Iliopoulou, T., Dimitriadis, P., Chardavellas, E., Dimitrakopoulou, D., Siganou, A., Markantonis, D., Moraiti, K., Kouros, K., Nikolinakou, M., and Koutsoyiannis, D.: Modelling water needs; from past to present. Case study: The Municipality of Western Mani, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-400, 2022.

Myriam Soutif-Bellenger, Guillaume Thirel, Olivier Therond, and Jean Villerd

The estimation of irrigation amounts and timings is crucial for the design of water management strategies at the regional scale. However, simplified modelling approaches are often preferred even though very complex and high-accuracy crop models or agent-based models exist. In this study, we develop a sensitivity analysis to evaluate the impacts of simplifications and hypotheses in irrigation modelling. For this, different simple modelling approaches based on the CropWat model were compared to a multi-agent based approach (Maelia), which served as a benchmark. To make an in-depth comparison between simulations, several indicators characterizing daily simulated irrigation were calculated and a decomposition of variance was carried out to measure impacts of diverse factors on irrigation. Applied over a downstream portion of the Aveyron River (southern France), the sensitivity analysis shows a high variability between simulations in function of modelling assumptions. It also shows that several simplifying approaches were able to reproduce the high-accuracy model estimation of irrigation. Decisive variation factors we identified are rules of triggering and quantification of daily irrigation, irrigation period definition and evapotranspiration estimation. Recommendations to take into account highlighted variability linked to farmers’ irrigation practices are introduced in this work, consisting in a combining a set of irrigation models. In function of advancement, a complete integrated agro-hydrologic modelling chain might be presented.

How to cite: Soutif-Bellenger, M., Thirel, G., Therond, O., and Villerd, J.: How much can we simplify irrigation in an integrated modelling purpose? A case study in southern France, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-32, 2022.

Léonard Santos, Guillaume Thirel, and Charles Perrin

Water management practices (dam management, uptakes for irrigation, industry and domestic water supply or water sanitation) can strongly influence river flow at the catchment scale. If water withdrawals and releases are important (for example in the case of a large dam), this influence can strongly impact the performance of bucket-type rainfall-runoff models whose structure do not explicitly consider water management practices. However, the influence of water management can also be compensated by the calibration of parameters, which is difficult to perceive when the model is conceptual, as the performance may not necessarily be negatively affected. This work aims at evaluating the effect of these compensations over the parameters of the GR4J bucket-type rainfall-runoff model over an influenced catchment. To do so, the model was applied in a semi-distributed way over the rainfed Sèvre Nantaise catchment in Western France. For this catchment, we used uptakes, sanitation and reservoir management data estimated at a daily time step, as well as a dense network of daily flow measurement stations. Water management practices were explicitly taken into account in the GR4J model through the airGR and airGRiwrm R packages that allow injecting or removing water from the river depending on water management practices. The model was calibrated on the different flow stations both with and without taking water withdrawals and releases into account. The obtained parameter values were compared in terms of reliability, robustness, plausibility and spatial homogeneity.

How to cite: Santos, L., Thirel, G., and Perrin, C.: Impact of water withdrawals and releases on the parameters of a bucket-type rainfall-runoff model, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-421, 2022.

Rajae El Aoula, Nadia Mhammdi, Laurent Dezileau, Gil Mahe, and Alexander Kolker

Recent reductions of sediment transport are observed in Bouregreg River and estuary close to the city of Rabat in Morocco. The cause of this evolution in sediment transport which may be due to human activities (dam, pollution), climate variability and natural events has been investigated from a paleo-hydrological approach. Sedimentological and geochemical analyses of slackwater flood deposits are used to assess the impact of a dam installed in 1974 and the climate change on the evolution of sediment transport during about 60 years. Higher accumulation rate of about 3,64 cm/year is observed between 1950 and 1978, whereas it was much lower about 0,41 cm/year between 1990 and 2017. This strong decrease in sediment rate appears much more due to the impact of dam construction rather than to climate change, however climate change in an increasing concern for the future.

How to cite: El Aoula, R., Mhammdi, N., Dezileau, L., Mahe, G., and Kolker, A.: Fluvial sediment transport degradation after dam construction in North Africa., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-520, 2022.