As nations plan to plant billions to trillions of trees to mitigate against climate change, it is essential to understand how large-scale re- or afforestation  will impact the Earth system. Trees remove carbon dioxide (CO2) from the atmosphere through photosynthesis and can store the sequestered carbon for centuries if not disturbed. This has climate benefits, as CO2 removal contributes to reduced atmospheric CO2 concentration and is a key measure for limiting global average temperature increase to 1.5 ⁰C or 2 ⁰C relative to pre-industrial conditions. However, despite this favorable biochemical effect of net tree cover increase, there are global and regional biophysical effects which remain understudied. One example of this is the impact of afforestation, reforestation, and avoided deforestation (referred to as forestation henceforth) on the atmospheric and terrestrial portions of the hydrologic cycle at the global and regional scales. This study uses a process-based modelling framework and relevant simulations from the World Climate Research Programme's Sixth Coupled Model Intercomparison Project (CMIP6) to quantify the global and regional impacts of realistic forestation on the global hydrologic cycle for a high-emissions shared socio-economic pathway to 2100 (SSP3-7.0). To accomplish this, the CMIP6 Land Use Model Intercomparison Project's afforestation experiment is leveraged. Changes in key hydrologic cycle variables and metrics such as precipitation recycling and soil moisture deficit are investigated. While the global impact of large-scale forestation on the hydrologic cycle is difficult to detect, regional impacts—often but not exclusively within the regions where forestation occurs—are apparent. Impacts on atmospheric and terrestrial hydrologic cycle variables can be seen with potential implications for water availability in some regions. Findings highlight the potential unintended consequences of including forestation in climate mitigation strategies. 

How to cite: Leclerc, C., Zickfeld, K., and Hahm, W. J.: Global and regional hydrologic cycle impacts of forestation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21027, https://doi.org/10.5194/egusphere-egu25-21027, 2025.

Understanding the spatial and temporal dynamics of drought is critical for addressing the growing challenge of water scarcity across Europe. This study employs the concept of landscape hydric potential (LHP) to regionalize European water retention and investigate the regions most affected by drought over time. Building upon insights from our previous work, "Rich North, Poor South - Regionalization of European Water Retention," we examine how hydric potential varies across Europe, with a focus on the Mediterranean and Eastern European regions where drought severity has intensified.

The analysis integrates long-term hydrometeorological data, land-use changes, and socio-economic drivers to determine the key factors influencing drought dynamics. We hypothesize that human activities—such as land use, water management practices, and urbanization—are significant amplifiers of drought presence, potentially outweighing natural climatic variability in some regions. By disentangling these drivers, we aim to provide a nuanced understanding of how anthropogenic impacts intersect with natural factors to exacerbate drought conditions.

Our findings highlight the urgency of sustainable land and water management policies to mitigate the effects of drought, particularly in vulnerable regions. Furthermore, the study underscores the value of the LHP framework in guiding regional adaptation strategies, fostering resilience to water scarcity, and ensuring equitable water distribution across Europe in the face of climate change.

How to cite: Lepeška, T., Wojkowski, J., Wałęga, A., and Młyński, D.: Environmental sensitivity and resistance to the intensity and frequency of drought phenomena in Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9613, https://doi.org/10.5194/egusphere-egu25-9613, 2025.

In the tropics, the strong seasonality of monsoon precipitation with recurring droughts leads to large uncertainties regarding evaporative water loss in regional water balances. To address these uncertainties, this study investigated the evaporation/inflow ratio (E/I) in the Deduru Oya basin in Sri Lanka. The investigation approach relies on a revised Craig–Gordon model with stable water isotopes (δ¹⁸O_H2O). A high-resolution survey was carried out, where river water samples were collected every two weeks near the river mouth during a hydrological year from November 2022 to October 2023. These fortnightly data show an overall trend of enrichment in ¹⁸O up to -1.4‰ due to the evaporation of surface waters in the basin. Based on these data, the calculated evaporation/inflow ratio (E/I) resulted in an evaporation loss of 10 ±1.2% for the entire catchment. This corresponded to 403 ±48 million m³ for 2022-2023. Meteorological factors such as temperature and humidity, as well as surface water storage and conveyance systems with many small reservoirs, were primary regulators of evaporative loss in the Deduru Oya River basin. This study provides an important dataset for a better understanding of the effects of the strong seasonality of the tropical climate and river morphology on water loss through evaporation. It lays a basis for further considerations of CO₂ uptake via water use efficiency.

Keywords: Craig–Gordon, evaporation, stable isotopes, surface water, seasonal effect

How to cite: Senarathne, S., van Geldern, R., Chandrajith, R., and A. C. Barth, J.: Effects of seasonality and cascading reservoirs on evaporative water loss in a tropical river basin: A case study from the Deduru Oya River Basin, Sri Lanka, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5031, https://doi.org/10.5194/egusphere-egu25-5031, 2025.

Urban flooding presents a complex challenge driven by urbanization, changing land use patterns, and climate variability, particularly in monsoon-dominated developing countries like India. According to the WMO, the world is rapidly urbanizing, especially in the flood plains. As a result, the global population is at risk, with the number of people living in flood-prone areas rising by 24% from 58 million to 86 million between 2000 and 2015. This study develops a comprehensive methodology for flood hazard mapping in the Bagjola area( Kolkata, India), integrating Markov Chain and Cellular Automata (Markov-CA) Land Use and Land Cover (LULC) prediction models with hydrodynamic simulations. The Markov-CA model predicted the 2050 land use changes after employing the land use data from 1990, 2005, and 2020. The predicted LULC changes were incorporated into the calibrated and validated MIKE+ hydrodynamic model (2020 data) for flood simulations, and the simulation results depicted the flood hazard maps, highlighting vulnerable areas under different land use scenarios.

The Markov-CA model achieved a Kappa coefficient of 0.84, indicating reasonably good agreement. The results reveal a growing trend of urbanization in the Bagjola Canal region, with 6.1% of vegetation and 29.06% of barren land projected to be urbanized by 2050 compared to 2020. Compared to the situations observed in 2020, under the future scenarios for 2050, the total flood hazard area is expected to increase by 15-40% in the Bagjola Canal region.

This methodology provides a practical framework for assessing the spatial impacts of urbanization on flood risk, offering valuable insights for urban planning and flood management in rapidly developing regions. The resulting floodplain and hazard maps can assist local municipal bodies in preparing flood mitigation and evacuation plans and serve as a criterion for property insurance evaluations.

How to cite: Kumar, A. and Remesan, R.: Integrating LULC Prediction and Hydrodynamic Modelling for Urban Flood Hazard Assessment: A Case Study of Bagjola, Kolkata, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19997, https://doi.org/10.5194/egusphere-egu25-19997, 2025.

Many alpine watersheds are complex and highly engineered systems designed to mitigate the risks associated with flooding and debris flows, thereby protecting downstream areas and safeguarding land. However, these engineering interventions often come with significant financial costs and environmental challenges. Thus, less engineered solutions which exploit the connections between land cover and hydrology-sediment functions to reduce risk need to be explored as alternatives. We develop and apply a novel approach that integrates forest dynamics into hydrological simulations within a landscape evolution model for Alpine watersheds.

We employ two simulation models: LandClim, a dynamic forest landscape model, and HAIL-CAESAR, a landscape evolution model. Integration between these models is achieved through two critical parameters: the m value and Potential Evapotranspiration (PET).

The m value in the HAIL-CAESAR model defines a soil scaling parameter which affects soil transmissivity and the soil water deficit in time, and thereby surface runoff and baseflow. This parameter was spatially implemented and calibrated based on hydrological response units combining soil and land use data. To investigate parameter robustness, we performed the calibration on 46 widely different catchments across Switzerland. We hypothesize that soil water storage capacity is greater in forested areas compared to pastures, agricultural land, and unproductive land, which leads to lower flood peaks and longer recession times.

The second key linkage vegetation dynamics and runoff is Potential Evapotranspiration (PET), which is calculated spatially and adjusted based on the forest leaf area simulated by LandClim. PET captures the maximum amount of water that can be lost to the atmosphere by evaporation and transpiration, thus directly impacting soil moisture levels and, consequently, the timing of surface runoff. By integrating PET into the landscape evolution model, we improved its accuracy in simulating hydrological processes, specifically enhancing our understanding how forest cover affects flow regimes.

Our findings highlight the role of forests in moderating flood peaks and timing in Alpine watersheds. We found a strong gradient of m values, with forests exhibiting slower transmissivity, which delays the onset of surface runoff. This helps to reduce and delay flood peaks, offering a natural buffer against extreme events. However, as saturation levels increase, this mitigation effect diminishes. We conclude that integrating forest dynamics into watershed management tools is a promising way to assess cost-effective and environmentally sustainable alternatives to conventional engineering approaches.

How to cite: König, L., Hands, T., Molnar, P., McArdell, B., and Bugmann, H.: Exploring the Influence of Forest Dynamics on Flow Regimes in Alpine Watersheds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9500, https://doi.org/10.5194/egusphere-egu25-9500, 2025.

“Human use of land has been transforming Earth's ecology for millennia” (Ellis, 2021).  Pressures on land are increasing due to land use and land cover (LULC) changes, such as deforestation, intensive agriculture and urbanization.  LULC changes significantly impact water both at the surface level and at the subsurface level – reduced infiltration and groundwater recharge, and increased runoff and pollution.  These LULC changes greatly impact long-term water availability, the quality of freshwater and ecosystem health.  Sustainable land planning has become necessary to mitigate the impacts of LULC change and to protect groundwater.  However, not all land planning projects are effective.  Therefore, evaluating them is crucial to determine whether they are actually effective for mitigation.

In response to the challenges of LULC change in the European Metropolis of Lille (Northern France), 12 LULC scenarios of actions were co-constructed with experts from different backgrounds. Our objective is to evaluate the possible effects on groundwater of actions suggested by the scenarios.

The evaluation of these scenarios will be accomplished, for example, by:

• Using indicators related to local conditions and available data;
• Integrating multidimensional welfare indices (Usubiaga-Liaño & Ekins, 2024) and the Doughnut Economics (Raworth, 2012);
• Quantifying the resulting indicators using GIS data, data from the literature and a capacity matrix (an ecosystem services evaluation tool used by the Hauts-de-France region) (Hérivaux & Farolfi, 2024).

The PICO will outline the various phases of the project and the tasks to be accomplished.  We invite you to visit our PICO and share your thoughts.  Your comments and suggestions on the project will be much appreciated.

Reference:

Ellis, E. C. (2021). Land Use and Ecological Change: A 12,000-Year History. Annual Review of Environment and Resources, 46(Volume 46, 2021), 1–33. https://doi.org/10.1146/annurev-environ-012220-010822

Usubiaga-Liaño, A., & Ekins, P. (2024). Methodological choices for reflecting strong sustainability in composite indices. Ecological Economics, 221, 108192. https://doi.org/10.1016/j.ecolecon.2024.108192

Raworth, K. (2012). A safe and just space for humanity: Can we live within the doughnut? Oxfam Discussion Papers. Oxfam International. https://policy-practice.oxfam.org/resources/a-safe-and-just-space-for-humanity-can-we-live-within-the-doughnut-210490/

Hérivaux, C., & Farolfi, S. (2024). Evaluation of Future Land Use Scenarios for Groundwater Protection and Territorial Sustainable Development [Poster]. IDIL Graduate Program, University of Montpellier. https://idil.edu.umontpellier.fr/files/2024/09/IDIL-Herivaux-Farolfi-LU-Scenarios-GW-protection-2024-07-16-1.pdf

How to cite: Promduangsri, P. and Hérivaux, C.: Evaluation of future land use scenarios for groundwater protection and territorial sustainable development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10199, https://doi.org/10.5194/egusphere-egu25-10199, 2025.

Evaporation serves as a crucial link among the global water cycle, energy cycle, and carbon cycle. The Complementary Relationship (CR), initially proposed by Bouchet in 1963, has been widely accepted as a tool for estimating actual terrestrial evaporation rates. However, its physical foundation has long been subject to scrutiny. This study aims to explore the thermodynamic basis of the CR based on the path of isenthalps and to propose a novel method for estimating actual evaporation rates under different land surface conditions. By examining the changes of air masses in the temperature-vapor pressure state coordinates and employing a first-order approximation, an analytical expression of the complementary relationship in thermodynamics has been derived. The current results indicate that, according to the derived analytical expression, actual evaporation can be determined by the temperature and vapor pressure states at the initial and final positions, with the process of change characterized by the coefficients defined in this study. Notably, the model performs optimally when the land surface is relatively moist.

How to cite: Li, G., Liu, W., and Zhang, B.: Thermodynamic insights into the complementary relationship and novel estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14469, https://doi.org/10.5194/egusphere-egu25-14469, 2025.

Water scarcity and availability represent two critical and interconnected facets of the challenges posed to agriculture by climate change. Among the components most affected by these changes are land use and landscape dynamics. The construction and intelligent management of the retention basins, reservoirs, drainage systems or water-saving soil management can mitigate water shortages during drought periods by enhancing storage and flow regulation.

This study uses the Wflow_sbm hydrological model, a distributed-parameter framework, to investigate how climatic condition and landscape factors influence water dynamics in a 60-ha experimental catchment in Lower Austria. By integrating comprehensive datasets from 2007 to 2024 and emphasizing key soil and land use characteristics, we aim to simulate the water balance across this historical change in land use, soil management, and crop rotation.

Previous investigations in this catchment lead us to assume that shifts in land use and agricultural practices will substantially impact runoff, infiltration, and evapotranspiration patterns. Furthermore, evolving rainfall regimes and rising temperatures driven by climate change are expected to increase challenges related to water availability. By analyzing these factors, the model scenario investigation seeks to highlight historical land use and structural changes and their effects on the water balance. This includes examining how past agricultural practices, and the landscape, and drainage systems have influenced runoff patterns, and evapotranspiration rates. Additionally, the study seeks to correlate these changes with historical climate data to identify long-term trends and thresholds in water availability.

This model application provides valuable insights into effective water resource management strategies amidst environmental changes. Future work will focus on quantifying the agrohydrological potential of further water-saving practices and extending the analysis to explore the broader ecological and community-level of land use and climate transformations.

Keywords: Wflow_sbm, hydrological modeling, land use change, climate change, water resources, experimental catchment

How to cite: Hussin, A., Brunner, T., Weninger, T., Fischer, K., and Strauss, P.: Exploring Land Use and Soil Management Impacts on Water Resources in a Small Austrian Catchment., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17786, https://doi.org/10.5194/egusphere-egu25-17786, 2025.

Extreme rainfall in mid-July 2021 led to flash floods in several catchments in Western Germany, such as the Inde catchment in the Meuse basin and the Ahr, Erft, and Wupper catchments in the Rhine basin. Record water levels exceeded historical data from gauging stations and extreme flood predictions. However, all four catchments experienced similar flooding in the past. Land-use and land-cover data (LULC) are key drivers for hydrological models. This study gathers historic LULC information for the 19^th century to quantify LULC-changes in the catchments and analyse their effects on flooding.

In the Erft catchment, flood damages are located in the upper catchment, as in Erftstadt-Blessem a 60 m deep gravel open pit mine near the river was flooded, and retained large amounts of discharge [1]. The upper catchment has been dominated by cropland since the early 19^th century (58%, vs. 48% today). Flooded areas in mid-July 2021 changed from mostly pastures (44%), to mostly urban fabric (41%).

The Inde catchment is characterized by industrial and mining activities. Urban fabric increased from less than 1% to 16% catchment-wide and to 37% in flooded areas. A lignite open pit mine at the mouth of the Inde River was flooded similarly to Erftstadt-Blessem [2].

Although reservoirs regulate the Wupper catchment, severe flooding also occurred in July 2021. In total, 11 out of 15 reservoirs exceeded their capacity limits. In this densely populated catchment, urban fabric increased from 5% to 29%, and reached 47% in flooded areas.

In the rural Ahr catchment, forest increased from 34% to 56%, and urban areas increased from less than 1% to almost 7%. In flooded areas, land-use changed from cropland to a 10-fold increase in urban fabric [3].

The four catchments differ in their geographical location (low mountain range vs, loess-dominated lowland) and their LULC-changes since the 19^th century. All catchments experienced severe flooding and damages during the July 2021 flood. Results indicate that catchment-wide land-use is not a key factor for flood severity. Rather, topographical and geological conditions and other factors, such as river regulation and damming, play a more significant role. However, increased anthropogenic pressure on floodplains led to higher water levels and an increased damage potential. In particular, urbanization and mining have emerged as critical contributors to flood severity. Thus, flood protection should consider land-use on floodplains and provide more space for the river.

[1] Lehmkuhl, F., & Stauch, G. (2023). Anthropogenic influence of open pit mining on river floods, an example of the Blessem flood 2021. Geomorphology, 421, 108522. https://doi.org/10.1016/j.geomorph.2022.108522

[2] Keßels, J., Wolf, S., Römer, W., Dörwald, L., Schulte, P., & Lehmkuhl, F. (2024). Enormous headward and gully erosion in a floodplain area reclaimed for open-cast lignite mining during the July 2021 flood in the Inde River valley (Western Germany). Environmental Sciences Europe, 36(1). https://doi.org/10.1186/s12302-024-00997-4

[3] Vélez Pérez, M., Wolf, S., Klopries, E.-M. (2023). Quantifizierung des Einflusses der Landnutzung an der Ahr auf das Abflussverhalten. Korrespondenz Wasserwirtschaft 7, 435-441

How to cite: Wolf, S., Han, L., Holste, I., Miller, J., Kleinewietfeld, I., Keßels, J., Lehmkuhl, F., and Schüttrumpf, H.: The extreme flood from mid-July 2021 in a historical context of land-use development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18425, https://doi.org/10.5194/egusphere-egu25-18425, 2025.

The EbroHydromorph project aims at studying the morphological changes of the middle Ebro River (between Logroño and La Zaida) in recent decades, and sediment transport in particular. In a first phase, a historical study of land use and land cover changes in the Ebro river basin to the end point of the study area is carried out, with an area up to 49,434 km², with the aim of finding out how these changes have affected the hydrogeomorphological conditions of the main river and its tributaries.

The elaboration of the cartography of the mid-20th century has been a laborious task carried out by digitalising land use and land covers (LULC) and completing it with some of the maps already drawn up previously in a few areas of the studied basin. This basin covers a very wide typology of landscapes, from Atlantic, to Mediterranean, including alpine and semiarid landscapes.

Land use and land cover distribution of the mid-20th century has been reconstructed and compared with that available in the 2014 land use and cover map, analysing in detail the modification of the active channel surfaces of the entire basin, as an indicator of the changes in flow and sediment inputs. The preliminary results show a drastic reduction of active channel surfaces, while forest, artificial and grassland areas have increased.

Additionally these land use and land use cover changes have been related to discharge evolution in those unregulated river reaches, in order to see the impact of LULC changes on flow availability.

How to cite: Ibisate, A., García-Rodríguez, S., Sáenz de Olazagoitia, A., Ballarín, D., Ormaetxea, O., Sánchez-Fabre, M., Ortiz de Arri, I., Mentxaka, G., Pirchi, V., García-Lagranja, J. M., and Ollero, A.: Land use and land cover change and river adjustment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20044, https://doi.org/10.5194/egusphere-egu25-20044, 2025.

Land cover influences surface water quality, as it affects the mobilization, deposition, and migration of ions through the landscape. In recent years, a large number of studies concentrated on the impact of the catchment's land cover on the water quality properties of inland water bodies in various temporal and spatial scales. Such studies, usually conducted on streams with the use of numerous land cover datasets, as well as different types of metrics, were not applied so far in the case of spring waters. In fact, the possibility of explaining the physicochemical characteristics of spring waters by land cover properties seems to be limited, as their water chemical composition is driven mainly by geological factors, such as duration of water circulation within the soil-rock matrix and type of the dominant minerals, and simultaneously, sometimes groundwater flow paths could be complicated, particularly in karst areas. However, definitely more favorable conditions for such investigations exist across lowland, post-glacial landscapes, where recharge areas of porous aquifers are spatially extended and relatively uniform in terms of sediments. Thus, the current preliminary study attempted to evaluate the relationships between the land cover and the hydrochemical properties of Quaternary spring waters. Field measurements (SEC, pH, and water temperature) and sample collection were conducted in November 2024 across 35 springs located in Mazovian voivodeship, draining sandy aquifers and laying over impermeable clays and loams. The concentrations of major cations and anions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, SO₄^2-, Cl^-, F^-) and selected trace elements (being anthropopressure indicators) in spring waters were determined using ion chromatography and ICP-MS, respectively. A circular geometric approach (500 m and 250 m radius) was adopted to calculate the land cover type contribution across spring recharge areas. In such delineated areas, Sentinel 2 Global Land Cover and Topographic Objects Database (BDOT10k) datasets were used for land use quantification (as percentages of artificial, cultivated, and forested areas), while the Spearman rank correlation coefficient was used for linking the land cover with ion concentrations. The investigated spring waters differed in terms of TDS (from 67 to 2052 mg/L) and hydrochemical types (from simple HCO₃-Ca to complex Cl-SO₄-HCO₃-Ca-Na). In the case of both datasets, it was documented that the type of land cover near the spring niche could act as proxy of their water chemical composition. Increased SEC values and Cl^-, K⁺, and Na⁺ concentrations were significantly (p<0.05) related with the higher participation of artificial areas, whereas  concentrations of NO₃^- were positively linked with the share of cultivated areas. Significant positive relationships were also documented between artificial areas and selected trace elements, such as boron, chromium, nickel, copper, selenium, and arsenic, being indicators of municipal and industrial pollution. The results suggest that the land cover of spring recharge areas in a lowland landscape could affect local groundwater chemistry, however, further studies are needed using more complex land cover metrics, particularly on the seasonality of the influence. 

How to cite: Łaszewski, M.: A First Insight into the Influence of Land Cover on the Hydrochemical Properties of Spring Waters Across a Lowland Landscape, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3284, https://doi.org/10.5194/egusphere-egu25-3284, 2025.

The Podhale region is one of the most popular tourist destinations in Poland. The most developed tourism services and infrastructure are based in Białka Tatrzańska. It’s home to a ski resort Kotelnica, which is known to use technical snow on their slopes. This village also has no proper water-sewage management, which may lead to the deterioration of surface water quality. The study aims  to demonstrate the human impact on the chemical composition and bacteriological contamination of the waters of the Czerwonka stream (in the longitudinal profile including waters from slopes), whose catchment area contains aforementioned resort.

Fieldwork involved measuring basic physicochemical parameters and collecting water samples for chemical composition and microbiological analyses. Ion chromatography instrument DIONEX ICS-2000 was used to identify 14 main ions and biogenic compounds (Ca, Mg, Na, K, NH₄, Li, HCO₃, SO₄, Cl, NO₃, NO_2, PO₄, F, Br). We measured TOC (total organic carbon), TIC (total inorganic carbon), TC (total carbon) and TNb (total bound nitrogen) with Elementar Vario TOC cube. Bacterial fecal indicators were determined using culture-based method on selective microbiological media to identify fecal pollution.

Along the 6 km stream, sharp increase in ion concentrations, particularly Na, K, SO₄, Cl, NO₃, NO₂, PO₄ was observed (20-21/10/2023). Concentration of Na ions is 32 times higher, while Cl concentration increased 79 times. TOC concentration is 16 times higher. Such inflation is due to anthropogenically impacted tributaries from the Białka Tatrzańska village, as well as groundwaters, showing the dual genesis of Czerwonka stream’s pollution. In particular, tributary coming from quite popular thermal baths is rich in sulphates and chlorides, with steady nitrate and biogenic compounds levels. The presence of numerous fecal bacteria in water samples indicates anthropogenic contamination of the stream waters.

How to cite: Kaflińska, O., Suwalska, W., Bojarczuk, A., Jelonkiewicz, Ł., Lenart-Boroń, A., Stankiewicz, K., Zalewska, J., and Żelazny, M.: The human impact on the longitudinal hydrochemical profile of the Czerwonka Stream in Białka Tatrzańska (Southern Poland, Podhale region), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3322, https://doi.org/10.5194/egusphere-egu25-3322, 2025.

Hydrological and chemical studies show that in addition to natural factors (geological structure, land cover), the chemical composition of water is strongly influenced by human activity. Typically, changes in physical and chemical characteristics during floods have been studied. It is worth noting that during non-flood days, when there are no floods, there are also changes in the chemical composition of the water. The aim of this study was to find out the changes in the concentrations of nutrients and forms of carbon in water in variously land used catchments during non-flood days.

The research was carried out from 4 to 8 July 2024 in small flysch catchment (22 km²) of Stara Rzeka located in the Carpathian Foothills in southern Poland. The study points were located in selected catchments with different land uses and anthropopressures: a forested catchment, an agricultural catchment and in front of and behind the Stara Rzeka stream wastewater treatment plant. Every 2 hours, water was sampled using an ISCO autosampler (n=100). In the laboratory, the concentrations of 14 ions (Ca, Mg, Na, K, NH₄, Li, HCO₃, SO₄, Cl, NO₃, NO₂, PO₄, F, Br) were determined by ion chromatography. In addition, results were also obtained for total carbon (TC), total inorganic carbon (TIC) and total organic carbon (TOC) (Vario TOC Cube).

The results show that in the forest catchment average concentrations of NO₃ were lower (1.82 mg·dm^-3) than in the agricultural catchment (36.32 mg·dm^-3). On the contrary, average TOC concentrations were higher in the forest catchment (4.56 mg·dm^-3) than in the agricultural catchment (1.42 mg·dm^-3). It is worth noting that the average TC concentrations were higher in the agricultural catchment (55.17 mg·dm^-3) than in the forest catchment (41.27 mg·dm^-3). Analysis of diurnal concentrations indicates that in the agricultural catchment, as water flow decreases, NO₃ concentrations increase, whereas as flow increases, NO₃ concentrations decrease. In the Stara Rzeka catchment, discharges of treated wastewater change the diurnal rhythm of nutrient compounds including: NO₃, PO₄, which is expressed in a greater amplitude of concentrations. In the longitudinal hydrochemical profile of the Stara Rzeka downstream of the sewage treatment plant, a rapid increase in concentrations of NO₃ and PO₄ was observed. Reference these diurnal concentrations of ions to the Polish ministerial regulation on water quality (Dz.U. 2021 poz. 1475) indicates that water taken at different times of the day (day/night) downstream of the wastewater treatment plant were of different quality (very good, good and below good status).

How to cite: Biernacka, A.: Diurnal changes of nutrients and carbon forms in different land use catchments located in Carpathian Foothills (Southern Poland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5274, https://doi.org/10.5194/egusphere-egu25-5274, 2025.

Catchments draining urban agglomerations are particularly exposed to significant anthropogenic pressure. Along watercourses, various types of wastewater are discharged, including both area pollution sources (e.g., parking lots, streets) and point sources, such as the discharge of treated wastewater from large municipal sewage treatment plants.

Field studies were conducted in Radom, along the Mleczna River, using the hydrochemical mapping method. Sixteen points and hydrological nodes were identified along the river's longitudinal profile, at locations where wastewater or other watercourses discharge. The studies were carried out twice (November 8-9, 2024), and 66 water samples were collected. During the fieldwork, selected physicochemical parameters (electrical conductivity, pH, dissolved oxygen content, and water temperature) were measured in two series, and water samples were taken for further laboratory analysis. In the laboratory, the chemical composition of 14 major ions (Ca, Mg, Na, K, NH₄, Li, HCO₃, SO₄, Cl, NO₃, NO₂, PO₄, F, Br) was analyzed using ion chromatography (DIONEX ICS 2000). The Elementar Vario TOC Cube analyzer was also used to determine the content of organic carbon (TOC), inorganic carbon (TIC), total carbon (TC), and total nitrogen (TNb).

Spatial variation analysis of physicochemical properties and ion concentrations indicates that anthropogenic influence is noticeable across all parameters along the longitudinal profile of the Mleczna River. It is worth noting that along the hydrochemical profile, there is primarily an increase in the concentrations of chloride and sodium. These ions are associated with the water and wastewater management of the city of Radom. This is especially evident at hydrological-chemical node number 9, where stormwater from the city’s drainage system is discharged. Anthropogenic pressure is reflected in a change in the hydrochemical type – particularly noticeable in the suburban area, where treated wastewater is discharged from the sewage treatment plant into the Pacynka River, a tributary of the Mleczna River (node 15). The natural hydrochemical type, related to the geological structure, changes from a typical, simple HCO₃-Ca type to a four-ion, complex HCO₃-Cl-Ca-Na type.

How to cite: Suwalska, W., Kaflińska, O., Maziarz, M., Poneta, T., Zalewska, J., Jelonkiewicz, Ł., and Żelazny, M.: Impact of Urban Agglomeration on the Longitudinal Hydrochemical Profile of the Mleczna River (Central Poland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19814, https://doi.org/10.5194/egusphere-egu25-19814, 2025.

Land use land cover (LULC) datasets serve as essential and foundational spatial information for a wide range of hydrological applications. However, the availability of these datasets from various sources, each employing different algorithms and techniques, poses a significant challenge for hydrological modelling. These variations can influence the identification of hydrological features and affect the accuracy of model simulations. This study aimed to comparatively assess and evaluate openly source available LULC products ESRI LULC, ESA World Cover LULC and Indian Space Research Organisation (ISRO)-Bhuvan for the simulation of watershed hydrology by setting up a hydrological model using Soil and Water Assessment Tool (SWAT). The evaluation was conducted for the Ong River watershed, a forest-cropland-dominated region within the Mahanadi River basin in India, covering an area of 4,650 sq. km. Various performance evaluation metrics were employed to assess the effectiveness of the LULC datasets, including Willmott's Index of Agreement, Nash-Sutcliffe Efficiency (NSE), Coefficient of Determination (R²), Percent Bias (PBIAS), and the RMSE-observations standard deviation ratio (RSR). Our research provides valuable insights for selecting appropriate LULC datasets for hydrological modeling, considering the unique characteristics of the catchment and the desired level of accuracy.

How to cite: Prashant, P., Kumar Mishra, S., and Kumar Lohani, A.: Evaluation of Open-source Land Use Land Cover products through SWAT Simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-799, https://doi.org/10.5194/egusphere-egu25-799, 2025.

This study assesses the impact of historical (1987–2018) and projected future (2018–2033) land use and land cover (LULC) changes on the water balance components of the Subarnarekha River Basin (SRB). The 2033 LULC spatial pattern was projected using the CA-Markov model, achieving a k-standard value of 0.7969, indicating high reliability for spatial and temporal change modelling. The SWAT model was employed to evaluate these impacts, calibrated and validated for 1987–2005 and 2006–2013, respectively. Model performance showed strong agreement between observed and simulated streamflow, with Nash-Sutcliffe efficiency ranging from 0.73 to 0.91 during calibration and 0.71 to 0.84 during validation across three sub-basins: Muri, Jamshedpur, and Ghatshila. Analysis revealed significant LULC changes, with dense and open forest areas declining from 17.49% to 6.71% and 11.60% to 8.04%, respectively, while settlement and agricultural areas expanded from 2.35% to 6.48% and 45.47% to 57.53%. These changes substantially impacted water balance components, leading to notable reductions in groundwater recharge and percolation, minimal changes in evapotranspiration and streamflow, and a considerable increase in annual surface runoff. Despite these shifts, changes in average annual water yield were minimal, underscoring the significant role of LULC dynamics in shaping hydrological processes within the SRB.

Keywords: LULC changes, SWAT model, water balance, CA-Markov model.

How to cite: Kumar, S. B. and Mishra, A.: Evaluation of the Impact of LULC Changes on Water Balance Components, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8160, https://doi.org/10.5194/egusphere-egu25-8160, 2025.

Land restoration often consists of tree planting and soil conservation measures to improve infiltration and reduce erosion. Tree planting has been shown to reduce annual water yields, but its effects on peak runoff during intense storms has been difficult to determine, particularly in large basins. Soil conservation measures, such as check dams, terraces, and runoff-trapping soil contours, are expected to reduce peak flows but their effects likely depend on precipitation intensity and antecedent moisture conditions. Here we use Ensemble Rainfall-Runoff Analysis to test how tree planting and soil conservation measures have affected storm runoff responses in five large-scale basins (774-17,180 km²) on the Chinese Loess Plateau. We find that peak runoff responses decreased by up to 86% following tree planting and associated soil conservation measures, and that this decrease was proportional to the percentage increase in the Leaf Area Index (LAI). The attenuation of peak runoff was much larger than the decrease in average runoff (59%) or median runoff (24%). The largest attenuation in peak runoff response occurred during high-intensity rainfall events. This observation implies that the decrease in peak runoff response cannot arise primarily from increased canopy interception or drier soils, because these would be expected to have a larger effect on lower-intensity events. Instead, we hypothesize that the main mechanisms are likely to be reduction in runoff-generating areas and increases in infiltration.

How to cite: Liu, S., Seybold, H., van Meerveld, I., Wang, Y., and W. Kirchner, J.: Tree planting and soil conservation measures have strongly attenuated storm runoff response on the Chinese Loess Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10122, https://doi.org/10.5194/egusphere-egu25-10122, 2025.

The Curve Number method, developed in the 1950s in the United States, is commonly used to estimate runoff depth resulting from heavy rainfall. Over many years, it has been tested in various regions and for different purposes beyond its original use. Despite numerous studies on this method, some issues still require consideration, i.e., a universally accepted procedure for CN determination from rainfall-runoff data. In this work, the authors attempt to estimate the CN parameter for a small, lowland catchment in central Poland. Historical data on catchment land cover and original rainfall-runoff measurements are used to determine the CN for three periods of different catchment land cover structures. Approaches for CN estimation are compared and discussed. The study states that a) over the period 1974-2018, a gradual increase in forest areas is observed, while the average CN parameter dropped from 59.6 to 55.9; b) among considered approaches, the least-squares calibration is a straightforward concept, allowing for reliable estimation of CN from rainfall-runoff data; c) further research is still needed to focus on the influence of actual initial losses on Curve Number value.

How to cite: Krajewski, A. and Hejduk, L.: Estimating Curve Number under changing catchment’s land cover structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11824, https://doi.org/10.5194/egusphere-egu25-11824, 2025.

Accurately modeling surface runoff is essential for effective water resource management, flood forecasting, and urban planning. This study refines surface runoff predictions in the Missouri Hydrological Area (MHA) using an enhanced Soil Conservation Service Curve Number (SCS-CN) method. Land use and land cover (LULC) data from 2001 to 2021 were analyzed to calculate weighted curve numbers, accounting for regional variability. Adjustments to the SCS-CN method, including improved formulations for initial abstraction, enhanced the predictive accuracy. The outputs were compared with observed and simulated surface runoff from the United States Geological Survey (USGS) and the North American Land Data Assimilation System (NLDAS), respectively.

To calculate the surface runoff, one of the major inputs is Curve Numbers (CN) which is predominantly based on land cover. The LULC analysis revealed that agricultural lands dominate the region, covering approximately 51% of the total area, followed by forests (30%), and developed or built-up areas (7%). Shrublands, grasslands, wetlands, and barren lands collectively account for the remaining area, with wetlands showing significant fluctuations due to environmental changes and restoration efforts. Weighted CNs were calculated for the study area, with values ranging from 30 to 98, depending on land use, soil type, and hydrological conditions. Agricultural lands and developed areas exhibited higher CN values, reflecting higher runoff potential, while forested and wetland areas had lower CNs, indicating greater infiltration capacity.

In addition to CN, precipitation is another input. Hourly precipitation data (0.125° × 0.125° lat/lon grids) are obtained from the NLDAS for the period January 2001 to December 2021. This dataset captures the region’s substantial variability, with annual precipitation ranging from 950 mm to 1,540 mm, reflecting distinct seasonal patterns and spatial heterogeneity within the study region.

The surface runoff estimated using the updated SCS-CN method was validated against the USGS Quick-Flow runoff estimates. Statistical metrics, including Nash-Sutcliffe Efficiency (NSE) and Kling-Gupta Efficiency (KGE), highlight the improved reliability of the enhanced method, with NSE and KGE values of 0.5608 and 0.4475, respectively, for the updated CN-formulation. In contrast, the original equation with the constant initial abstraction ratio of 0.2 yielded lower NSE and KGE values of 0.4055 and 0.1763. These results emphasize the importance of refining CN estimates, which explains more variance, and aligns more closely with observations. This adaptability to regional hydrological conditions makes the enhanced method a choice for accurate surface runoff predictions.

How to cite: Abeysinghe, U., Pelletier, C., and Aloysius, N.: Refining Surface Runoff Predictions in Missouri, United States Using Enhanced SCS Curve Number Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12485, https://doi.org/10.5194/egusphere-egu25-12485, 2025.

Due to the increasing duration and magnitude of both agricultural and hydrological droughts, farmers face the problem of declining yields and reduced irrigation possibilities. In our recent study (Heinz et al. 2025, under review), we found that increasing soil organic carbon (SOC) could increase soil water retention and thus mitigate yield losses during a recent drought year. However, it is unclear how the accumulation of SOC in agricultural soils could affect hydrological processes on the catchment scale.

Local- to regional-scale changes in land use, such as afforestation, or structural changes, such as terracing or check dams, on catchment scale hydrology have been widely studied (Farley et al. 2005; Deng et al. 2021). The effects of agricultural management adaptations at the field scale are less well understood. However, for example, the effect of switching to conversational tillage as a soil conversation measure is thought to reduce flood peaks and increase rise times (Samanta et al. 2023), highlighting the need for further research.  In this study, we address a major research gap by assessing the influence of increasing SOC on catchment-scale hydrology using the Mesoscale Hydrological Model (mHM). The study focuses on the mid-sized Broye catchment in western Switzerland, where mHM was applied with the novel subcatchment conservation module SCC, which significantly improved the simulations (Shrestha et al. 2025, under review).

In the SOC-increase scenario, we assess the impact on key hydrological fluxes (e.g. evapotranspiration, percolation, groundwater recharge) and reservoirs (e.g. soil water storage), as well as the overall water balance and discharge dynamics.

Preliminary results indicate that while SOC enhancement causes measurable changes in soil water storage and fluxes at smaller scales, its overall effect on catchment scale water balance and discharge is limited. These modest effects may be due to physical insensitivity of large-scale hydrological processes but may also be due to model limitations in parameterisation and representation of localised changes. This will be subject to further analysis, as will the assessment of the effect of increased SOC on peak and low flows.

References:

Deng, C., G. Zhang, Y. Liu, X. Nie, Z. Li, J. Liu and D. Zhu (2021). "Advantages and disadvantages of terracing: A comprehensive review." International Soil and Water Conservation Research 9(3): 344-359.

Farley, K. A., E. G. Jobbágy and R. B. Jackson (2005). "Effects of afforestation on water yield: a global synthesis with implications for policy." Global Change Biology 11(10): 1565-1576.

Heinz, M., M. E. Turek, B. Schaefli, A. Keiser and A. Holzkämper (2024). "Can adaptations of crop and soil management prevent yield losses during water scarcity? - A modelling study [Preprint]." EGUsphere 2024: 1-33.

Samanta, S., S. Ale, D. K. Bagnall and C. L. S. Morgan (2023). "Assessing the watershed-scale effects of tillage management on surface runoff and sediment loss using a Curve Number-precipitation relationship based approach." Journal of Hydrology 625.

Shrestha, P.K., Samaniego, L., Rakovec, O., Kumar, R., and Thober, S. (2025)(under review). “Enhancing Global Streamflow Modeling to Enable Locally Relevant Simulations”. Water Resources Research.

How to cite: Heinz, M., Holzkämper, A., Ledain, S., Horton, P., Kumar, R., and Schaefli, B.: From Field to Catchment: Evaluating the Hydrological Effects of Soil Organic Carbon Increases with the distributed mesoscale hydrologic model mHM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18191, https://doi.org/10.5194/egusphere-egu25-18191, 2025.