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This paper develops a discharge allocation model for public water supply for a set of communities, considering available and planned reservoirs and interbasin transfer projects. Reservoir operation rules were defined for maximum water withdrawals in function of the storage volume over a period of 45 years, and then the discharges to be transported from the different sources to 18 locations were defined, minimizing the costs. Generalized Reduced Gradient and Particle Swarm Optimization algorithms were used in the optimization processes. The model was applied in the Agreste region of the state of Pernambuco, Brazilian semiarid. This region has the worst water balance in the entire country and three interbasin water transfer systems are under construction. Due to the interconnection among the systems, it will be possible to supply the communities from one or another source. The results showed that the optimized operation of the reservoirs can minimize water transfer and costs. [ABSTRACT FROM AUTHOR]

Large volumes of water evaporate from reservoirs in arid and semi-arid regions. Such water losses are substantial in the regional water balance, and must be considered in the management of water resources. This paper evaluates 12 reservoir evaporation methods that are applied to calculate daily evaporation from Karkheh reservoir (Iran) created by the world's sixth largest dam. The Bowen ratio energy budget (BREB) formula is chosen as the reference method for the purpose of evaluating 12 alternative evaporation methods. The evaporation methods are ranked based on their accuracy, sensitivity to input variables, and simplicity of application by means of the technique for order of preference by similarity to ideal solution (TOPSIS) multi-criteria decision analysis method. Our results from a multi-year data set for Karkheh reservoir indicate that the best-ranked methods by TOPSIS considering the performance indices are the solar radiation-temperature based methods and the Blaney and Criddle method that is based on temperature and daylight duration variables. [ABSTRACT FROM AUTHOR]

This study examines the influence of human activities and climate variability on 86 dams and hydropower across Iran. The term 'mirage water' is introduced to estimate the impact of these factors on inflow. Data analysis shows that out of 1729 m3s−1 of mirage water, 705 m3s−1 are contributed by anthropogenic activities and 1024 m3s−1 by precipitation deficits. This indicates that some parts of Iran's strategic investments in water resources management over the past 60 years have failed. The study underscores the necessity for enhanced management practices and infrastructure investments to ensure sustainable water resources in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Since the 1970s, the Government of Ethiopia has implemented villagization, whereby nomadic pastoralist groups are supported to develop (more) sedentary lifestyles and livelihoods. Villagization has been officially promoted to encourage diversification from livestock herding to agricultural cultivation, and to fulfil basic needs through infrastructure and services. From the late 2000s, villagization was reintroduced for arid and semi-arid regions as a strategy for adaptation to climate change, as part of the country's green growth agenda. The aim of this paper is to evaluate to what extent this phase of villagization has contributed to adaptation strategies among pastoral and agro-pastoral communities, based on an empirical analysis of four villagised sites in the Middle Awash Valley using qualitative data collected between 2014 and 2018. Perceptions and experiences of villagization varied across individuals, households, villages, and districts. While villagization has generally delivered infrastructure and services, and offered income diversification to those able to access irrigated agriculture, its implementation has been partial and uneven, and it has reproduced previous problems of resource scarcity while creating new risks and vulnerabilities. We argue that villagization may play a role in some aspects of adaptation, if programmes address the drivers of livelihood change, and embed equity and rights. [ABSTRACT FROM AUTHOR]

The agricultural expansion in Abu Dhabi Emirate has increased the pressure on the emirate's groundwater reserves, with projections that they will be completely depleted within a few decades. This study quantitatively examines the impacts of current farming practices on the sustainability of groundwater resources. Participants from 344 farms were surveyed. The study found that 76% of the farms rely on groundwater as their main source of water, with significant occurrence of low water productivity. The findings highlight the need to develop and implement effective strategies to maintain the sustainability of groundwater and agricultural development. [ABSTRACT FROM AUTHOR]

Groundwater has become an alternative water supply for various sectors of the population and the economy, and its extraction is increasing worldwide. The water poverty index (WPI) is a holistic tool that enables the establishment of links between poverty, social marginalization, environmental integrity, water availability and health. The index includes five components – water resources, access, capacity, environment and use – which are evaluated on a scale of 0 to 100. The objective of this research is to calculate the WPI by applying remote perception techniques to the environment component. Through multi-temporal analysis, we estimate the variability of soil cover in a semi-arid area of San Luis Potosí in Mexico, where the available surface water and groundwater is mainly for agriculture. The overall result for the studied area was a WPI of 56, which reflects contradictions in the management of the resource that is abundant. [ABSTRACT FROM AUTHOR]

The use of saline groundwater in irrigation due to the limited availability of fresh water is one of the main causes of land degradation in arid and semi-arid environments. The agro-ecosystem of Siwa Oasis was monitored over a period of two decades. A stable isotope study, oxygen-18 and deuterium, indicated that Siwa groundwater is of meteoric origin. Siwa has two groundwater aquifers: a shallow limestone aquifer, LA, with highly saline water (Total Dissolved Solids, TDS, up to 6848 mg/L), and a deep Nubian sandstone aquifer, NSA, containing fresh water (TDS 192–256 mg/L). The sodium adsorption ratio, SAR, of LA water is high with an average value of 13.9 while the SAR of NSA water is low with an average value of 2.1. Schoeller and Piper's diagrams showed that LA water was of sodium, chloride-sulfate type, while the NSA water was classified as sodium carbonate and bicarbonate water type. Saturation Index (SI) calculations showed that both the LA and NSA water were undersaturated to halite minerals. Consequently, there is room to accommodate extra Na+ and Cl− from halite. Most Siwa land is irrigated with LA water due to low drilling costs. LA groundwater and Siwa soils were found to be deteriorating dramatically and the average water and soil salinity increased by 30–36% per decade. No change in NSA water quality was recorded over the same period. Interventions for the restoration of the deteriorated Siwa ecosystem are summarized. The approach conducted in this study can be repeated in similar ecosystems. [ABSTRACT FROM AUTHOR]

In semi-arid regions, reduced river flows present is a major challenge in water resources management. We present a new standardized contribution of rainfall to runoff index (SCRI) for evaluating changes in rainfall contribution to river flow. We employ the standardized precipitation index (SPI), standardized discharge index (SDI) and SCRI to characterize meteorological drought, hydrological drought and land-use change impacts on river flow, respectively. These indices are applied to the Mond River Basin (Iran), which is regulated by the Salman Farsi and Tangab dams since 2006. A new concept called "mirage water" is proposed that represents the reduced water delivery to downstream areas due to new developments and water withdrawals in headwater tributaries. In particular, mirage water accounts for changes in upstream water consumption between the planning phase and construction/operation life of dams. We recommend that this concept be used for communication with decision-makers and managers to clarify the need for revising dimensions of planned dams. [ABSTRACT FROM AUTHOR]

Evapotranspiration plays a crucial role in the surface hydrothermal balance. On a regional scale, especially in the blown-sand areas, an accurate estimate of evapotranspiration has important guiding significance for a rational allocation of water resources and drought monitoring. The objective of the study is to estimate the surface evapotranspiration for the blown-sand region in the Ordos Basin based on the Surface Energy Balance Algorithm for Land (SEBAL) model using six phases of Landsat 8 remote sensing images during 2015-2016 and the corresponding surface meteorological observational data, analyze the characteristics of temporal and spatial distributions of evapotranspiration in the study area. The results show that (1) the daily evapotranspiration presents a seasonal variability with the highest in summer, lower in autumn and spring, and the lowest in winter; (2) the evapotranspiration is distinctly characterized by its spatial variability, which is related to the terrain and geomorphology in this area as well as the effect of human activities; and (3) the daily evapotranspiration estimated by the SEBAL model was validated using the Food and Agriculture Organization (FAO) Penman-Monteith (P-M) model, which yielded an mean relative error (MRE) of 19.5%. In summary, the remote sensing data based SEBAL model can be applied to robustly estimate evapotranspiration for the blown-sand regions, and the study results can be served as an important reference for the research of water circulation, rational utilization of water resources, and protection of the ecological environment in the arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Poor water resource management is an important factor in soil salinization in arid areas. In this study, the status of soil salinization and its controlling factors are summarized for the Yinchuan Plain, North-West China. The conjunctive use of surface water diverted from the Yellow River and groundwater abstracted from a shallow aquifer is proposed to alleviate soil salinization in the plain. Scenarios are designed and simulated to determine the optimal proportions at which groundwater should be exploited for irrigation in the three cities of the plain. Policies and suggestions regarding sustainable water resources and soil salinization research in the plain are recommended. [ABSTRACT FROM AUTHOR]

Current water demand management of megacity-dominated areas in arid-zones should be revised to optimize water allocation for sustainable development. A novel hierarchical optimization model is proposed and examined for such an area in the arid zone of Iran. The model can significantly increase water economic efficiency, reduce unsatisfied demand, and maintain necessary agricultural production. Model sub-optimization provides the cropping pattern and transient four-phenological-stage deficit-irrigation strategy that maximizes economic benefit per unit agricultural allocation. The model employs a nonlinear benefit function for industry, a linear benefit function for service, and a cubic benefit function for deficit-irrigated agriculture. If available water is unchanged, optimal economic benefit increases 283 percent from the current situation. This requires decreasing agricultural water allocation, changing cropping patterns, using deficit irrigation, and increasing development of industrial and service sectors. If annual available water decreases by 25%, or by 40%, net economic benefit can increase 101% and 19%, respectively. [ABSTRACT FROM PUBLISHER]