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The paper seeks to gain greater water literacy and numeracy in the connections between water and Regenerative Agriculture (RA). By identifying the many roles and quantities of water and soil-water, our paper argues that water is the Achilles Heel of RA.  At a basic level, RA is failing to fully appreciate and incorporate the many varied inputs, processes and outcomes of water. In ‘outcome’ terms, RA intends to improve soil-water properties and catchment hydrology so that, for example, rainfall seeps into soils rather than running off land surfaces.  In ‘process’ terms, RA adopts agricultural practices such as maintaining a protective cover that aims to enhance soil physical fertility (such as bulk density) and soil-water properties such as infiltration and available water holding capacity.  While these outcomes and processes are idealized and laudable, they miss the many ways in which water and RA intersect. For example water and hydrology are not only affected by RA, but water is also an input to RA. The latter is necessary when soil moisture is required to bolster soil organic accumulation and biological activity.  Accordingly, we find two interconnected fault lines. First, the descriptive and quantified roles of soil-water and water in RA are often missing or poorly explained, and secondly, narrative tropes and terms (e.g. ‘net zero’ or ‘net positive’ water) for describing the benefits and aims of RA are, at best, lacking context or, at worst, are misleading and incorrect. We conclude that scientists and decisions-makers should more thoroughly interrogate how RA is being applied in the context of basin water availability and attempt to bring more precision in regards to quantities of water required – and recognize the competition for those resources as well as opportunity costs. How those quantities overlap with local policies, allocations and hydrology, including farmers’ individual views and policy choices, are critical to RA success. 

How to cite: Lankford, B. and Orr, S.: Is Water the Achilles Heel of Regenerative Agriculture?  A critical examination of the roles and omissions of soil-water and water in ‘Regen Ag’, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-510, https://doi.org/10.5194/iahs2022-510, 2022.

Climate change manifested in Ukraine by rapid (over 0.6^oC in 10 years) increase in average annual air temperature causes a progressive deterioration of natural water supply significantly increasing the need for irrigation to ensure sustainable agriculture.

"Irrigation and Drainage Strategy in Ukraine until 2030" provides for an  increase of irrigated lands area up to 1.5-1.7 million hectares and the corresponding significant increase in water consumption from the current 1.5-1.8 billion m³ to 5-6 billion m³. Given that climate change has a negative impact not only on the state of natural water supply, but also on the state of available water resources, their rational use in irrigation is an important component of sustainable water management.

Effective tools for its implementation in irrigation are decision support systems. Their usage provides a capability to achieve maximum irrigation efficiency when complying with the following provisions:

- Irrigation should maintain root layer moisture content in a narrow range of high values (from 0.8-0.85 of field capacity to field capacity);

- Tensiometric pressure should be used as a criterion of moisture content and moisture availability for plants;

- Water retention curves should be used to determine field capacity, pre-irrigation thresholds, and optimal ranges of moisture available to plants;

- Moisture transfer models for saturated-unsaturated soils stated in terms of pressure can accurately predict irrigation schedules and rates;

- The combined use of several methods for evapotranspiration assessment improves the accuracy of calculations;

- Remote sensing data can be used to tranfer irrigation schedules and rates predictions to the areas not covered by instrumental monitoring tools.

The application of these principles provides for

- an increase in crop yields accompanied by irrigation water volumes reduction;

- irrigation with environmentally friendly rates minimizing water losses for infiltration, and the development of flooding and secondary salinization processes.

The introduction of these principles in practice will increase the sustainability of water management in agriculture in the conditions of climate change, and the use of decision support systems at full scale will ensure the maximal materialization of the potential of crops’ varieties and hybrids.

How to cite: Romashchenko, M., Bohaienko, V., Matiash, T., Shatkovskyi, A., Kolomiets, S., and Danylenko, I.: Conceptual principles of water resources management in irrigated agriculture, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-551, https://doi.org/10.5194/iahs2022-551, 2022.

Drainage is the water flowing under the roots when the soil's capacity to hold water is exceeded. It is an important term of the crop water budget, controlling soil salinization, potentially impacting downstream ecosystems, and being a strong indicator of water productivity. Estimating this flux at spatial scales relevant to farmers (plot-scale) and to watershed or irrigation district managers (sub-basin-scale) is thus fundamental for a sustainable management of water, soils, and downstream rivers. However, even though it can be measured or estimated locally with lysimeters or physically-based models, respectively, drainage is generally neglected or considered as a residual variable in crop water balance models. Furthermore, many studies have shown the relevance of using remote sensing data to spatialize crop water fluxes. The aim of this work is thus to estimate drainage from the plot-scale to the sub-basin-scale by using a crop water balance model coupled with remote sensing observations. For this, SAMIR, a crop water balance model based on the FAO-56 method using remote sensing data to constrain the modeled vegetation and the soil water status, is used. The approach is tested over the Algerri-Balaguer irrigation district in northeastern Spain where in-situ drainage measurements are available at an integrated (sub-basin) scale. Those data were obtained from a network of drains feeding four outlets where the drainage is continuously measured. Additionally, four lysimeters were installed on two experimental fields of the area. Firstly, the drainage simulated by SAMIR and by a physically-based model (HYDRUS-1D) are compared with the lysimeters measurements. Preliminary results indicate that both models are able to reproduce the drainage amount cumulated over the season given a site-specific calibration. Secondly, the field-scale SAMIR drainage estimates are aggregated over several sub-basins and compared against the drainage measurements at the outlet of the associated sub-basins. A strategy for calibrating SAMIR at the sub-basin-scale is proposed. The obtained results provide a first assessment of the potential of using a satellite-driven crop water balance to retrieve agricultural drainage at multiple spatial scales.

How to cite: Laluet, P., Olivera Guerra, L. E., Altés Gaspar, V., Rivalland, V., Simonneaux, V., Bustillo, V., Bellvert, J., Villar, J. M., and Merlin, O.: Estimating the drainage of irrigated areas: a combined crop water balance modeling and remote sensing approach, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-232, https://doi.org/10.5194/iahs2022-232, 2022.

The oases of the pre-Saharan basin of Wadi Ferkla in southeastern Morocco receives low and erratic rainfall (average of 141 mm/year and inter-annual standard deviation of 70 mm - Ait-Bouijane rain gauge over the period 1961-2018). From the 70's, surface and groundwater are increasingly used due to the expansion of irrigation, mainly along two wadis, namely Wadis Ferkla and Satt originating in the High-Atlas and the Anti-Atlas Mountains, respectively. Their flows reach the Ferkla’s irrigated perimeters only when the volume of the flood events exceed upstream evaporation, withdrawals and riverbed's infiltration.

Nowadays, these irrigated perimeters exert significant pressure on groundwater resources, through numerous drillings equipped with pumping systems, most of them are powered by solar energy. This unsustainable situation incentivizes individual farmers to design and implement innovative technics to increase water access for their farms. For instance, the spreading of floodwaters - an ancestral and collective irrigation practice in traditional oases - is currently being adopted and adapted by individuals at the farm level. The technique consists on partially diverting flood flows into earthen basins. The stored water either infiltrates to recharge local aquifers, or is pumped for flood irrigation of date palms.

An experimental protocol was set up to characterize groundwater recharge below one of these on-farm basins equipped with a recharge well. Barometric probes were installed in the basin, in the recharge well and in neighboring boreholes to automatically monitor water table levels (10-minute-time-step). Manual measurements were performed regularly to calibrate the monitoring probes. A topographic survey of the monitoring points and of the basin aimed at deriving piezometric levels from water levels measurements and estimating the height-surface-volume curves of the basin. After 7 months of continuous monitoring, 3 flood events were recorded. The establishment of the basin water balance at a fine time-resolution allowed estimating its different components including the infiltration rate influencing groundwater recharge. An Analytical modeling of this process was developed to explore alternative design and management options of the basin. This approach aims to contribute to a broader reflection on securing water management in this fragile oasis ecosystem.