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Water sustainability involves several natural and human spheres conditioning the availability and quality of water resources and life conservation. Regarding water quality, currently emerging pollutants (EPs) are a key topic at global scale since they are difficult to remove by traditional water treatment systems. In this context, this work aims to evaluate experts’ perception of several EPs issues with a special focus on semi-arid Mediterranean areas where EPs are negatively impacting water, environmental, and agricultural systems as, in these areas, effluents from water treatment plants are widely reused in the irrigation of crops, urban gardens, and golf courses or directly discharged on natural streams. Particularly, a detailed survey composed of questions about EPs regulation, risk insight, equipment, social and economic impacts, was performed collecting 437 responses. Main results suggested that EPs existence may pose a significant risk and a destabilizing factor in wastewater reuse, with negative impacts to crop irrigation, being managers the class with more concern followed by scientifics and administratives. New EPs regulations raises uncertainty amongst experts since 29 % considered positive its creation, while 20 % estimated this fact as regular and 14 % as negative. As well, although the combination of technologies to improve EPs removal generated agreement, aspects like the treatment charges at water treatment plants or the price/bill of EPs-free water were features of ambiguity. Within EPs elimination, the three expert groups highlighted that technologies impacts in the sustainability spheres will be positive on public health (87 % of responses), social trust (75 %), and environmental sustainability (76 %). Likewise, 88 % of experts concurred that the future of wastewater reuse relies on a combination of technologies. These findings offer valuable information to water legislators and policymakers to manage water resources, especially in semi-arid areas due to the final use of treated effluents and, therefore, the great implications for agriculture, environment and human health.

Freshwater shortages in the Middle East and North Africa's region (MENA) cause serious issues, while climate change causes even more issues. The current study examines how climate change may impact future irrigation requirements in Egypt's Upper Region using the medium greenhouse emission RCP 4.5 and high emission RCP 8.5 scenarios. Based on the Intergovernmental Panel on Climate Change (IPCC) and the Fifth Assessment Report, the climatic projections for RCPs 4.5 and 8.5 for the years 2023–2080 and 2081–2100 were used to determine the patterns of temperature and rainfall in the upper Egypt territory. The CROPWAT model was employed to estimate reference evapotranspiration (ETo) and net irrigation water requirement (NIWR) for the upper Egypt territory key crops sugar cane, potatoes, berseem clover (alfalfa), dry bean, wheat, cotton, maize, and tomato based on the predicted meteorological conditions. Five different scenarios for the key crops' future irrigation needs were calculated. The results reveal that under RCP 4.5 greenhouse emission for the periods 2023–2080 and 2081–2100, respectively, the overall NIWR for all examined crops increases by 5.1 and 5.9% in comparison to the current (2022) total NIWR for all crops. The total NIWR for all crops analyzed increases by 7.7 and 9.7% under the RCP 8.5 greenhouse emission scenario for the periods 2023–2080 and 2081–2100, respectively, in contrast to the current total NIWR for all crops. It is important to consider changes in water resource management in the MENA region, such as applying modern irrigation systems, using crop pattern rotation strategies with minimal water demands, and changing crop calendars or the times and locations of cropping activities. [ABSTRACT FROM AUTHOR]

We consider a simple crop irrigation model and study the optimal control which consists of maximizing the biomass production at harvesting time. A specificity of this work is to impose a quota on the water used for irrigation, in a context of limited resources. The model is written as a 2d non‐autonomous dynamical system with a state constraint, and a non‐smooth right member given by threshold‐based soil and crop water stress functions. We show that when the water quota is below the threshold giving the largest possible production, the optimal strategy consists of irrigating once. We then show that the optimal solution can have one or several singular arcs, and therefore be better than simple bang‐bang controls, as commonly used. The gains over the best bang‐bang controls are illustrated on numerical simulations. These new feedback controls that we obtain are a promising first step towards the concrete application of control theory to the problem of optimal irrigation scheduling under water scarcity. [ABSTRACT FROM AUTHOR]

Semi-arid regions often face severe drought events that reduce agricultural and livestock production. In recent years, some international studies have used multicriteria decision analysis (MCDA) approaches combined with geographic information systems (GIS-MCDA) to support decision-makers in assessing the suitability of agricultural land for irrigation in semi-arid regions. Unlike previous studies, which have only considered a single source of water for crop irrigation, this study proposes a GIS-MCDA approach that considers all potentially available local water sources (e.g., groundwater, surface water, and wastewater) as possible alternatives for better multisource water resource management (MWRM) in regions facing water shortages. The geospatial multicriteria evaluation implemented in this study considers a series of technical, environmental, and agricultural productivity criteria using the analytical hierarchy process (AHP) method. Three independent baseline maps were generated, showing the spatial distribution of suitable areas for crop irrigation for each considered water source in the studied area. Surface water, groundwater, and wastewater offered suitable crop irrigation for 83%, 70%, and 26% of the study area, respectively. Overlapping these areas produced a final map showing all the feasible areas for each crop irrigation alternative at the same time. The MWRM approach considering all water sources increased the coverage of suitable areas to be irrigated in the study area by 2.2%, 20.4%, and more than 225% compared to considering surface water, groundwater, and wastewater, respectively, independently. The GIS-MCDA framework proposed in this study provides better support for decision-makers and stakeholders, favouring a reduction in possible conflicts over water scarcity, the diversification of irrigated crops, and an improvement in the quality-quantitative management of water resources in semi-arid regions. • A GIS-MCDA approach to assess the suitability of agricultural lands for irrigation. • Three sources of water were considered in the approach for better water management. • Analysis of combined water resources increased the resulting areas suitable for irrigation. • The proposed analytical approach provides better support for irrigation in semi-arid regions. [ABSTRACT FROM AUTHOR]

Climate change is a proven fact. In the report of 2007 from IPCC, one can read that global warming is an issue to be dealt with urgently. In many parts of the world, the estimated rise of temperature (in a very near future) is significant. One of the most affected regions is the Iberian Peninsula, where the increasing need for water will very soon be a problem. Therefore, it is necessary that decision makers are able to decide on all issues related to water management. In this paper, we show a couple of mathematical models that can aid the decision making in the management of an agricultural field at a given location. Having a field, in which different crops can be produced, the solution of the first model indicates the area that should be used for each crop so that the profit is as large as possible, while the water spent is the smallest possible guaranteeing the water requirements of each crop. Using known data for these crops in Portugal, including costs of labour, machines, energy and water, as well as the estimated value of the products obtained, the first mathematical model developed, via optimal control theory, obtains the best management solution. It allows creating different scenarios, thus it can be a valuable tool to help the farmer/decision maker decide the crop and its area to be cultivated. A second mathematical model was developed. It improves the first one, in the sense that it allows considering that water from the rainfall can be collected in a reservoir with a given capacity. The contribution of the collected water from the rainfall in the profit obtained for some different scenarios is also shown. [ABSTRACT FROM AUTHOR]