Socio-Economic Impact of Evaporation Losses from Reservoirs Under Past, Current and Future Water Availability Scenarios in the Semi-Arid Segura Basin

This study assesses evaporation losses from water reservoirs in the semi-arid Segura basin (south-east Spain), one of the most water stressed European catchments. These losses are evaluated from both the hydrologic and economic perspectives under different water availability scenarios that are based on water policy trends and climate change predictions. We take a multidisciplinary approach to the analysis, combining energy balance models to assess the effect of climate change on evaporation from water bodies, Class-A pan data and pan coefficients to determine evaporation loss on a regional scale, and non-linear mathematical programming modelling to simulate the economic impact of water use and allocation in the basin. Our results indicate that water availability could be reduced by up to 40 % in the worst-case scenario, with an economic impact in the 32–36 % range, depending on the indicator in question. The total annual evaporation loss from reservoirs ranges from 6.5 % to 11.7 % of the water resources available for irrigation in the basin, where evaporation from small reservoirs is more than twice that from large dams. The economic impact of such losses increases with water scarcity, ranging from 4.3 % to 12.3 % of the value of agricultural production, 4.0 % to 12.0 % of net margin, 5.8 % to 10.7 % of the irrigated area, and 5.4 % to 13.5 % of agricultural employment. Results illustrate the importance of evaporation losses from reservoirs in this region and the marked upward trend for future scenarios. Besides, they highlight the extent of the impact of climate change on future water resources availability and use in southern Europe.     

A Modelling Approach to Forecast the Effect of Climate Change on the Tagus-Segura Interbasin Water Transfer

This study was conducted in the upper Tagus River basin (UTRB), whose available water resources are partially transferred from the Entrepeñas and Buendía reservoirs after local needs satisfaction to the Segura River basin using the Tagus-Segura water transfer (TSWT), the largest hydraulic infrastructure in Spain. This study evaluates the climate change impact on the TSWT by considering future evaporation rates and bathymetric changes in the Entrepeñas and Buendía reservoirs. The findings of this study indicate a consistent decline in precipitation and an increase in temperature and evaporation under all climate impact scenarios. Consequently, inflows to the reservoirs will decline by 19% (RCP 4.5) and 53% (RCP 8.5) for 2070–2099, which could reduce water volumes that could be transferred to the Segura basin by more than 60%. The simulation of the TSWT operation rules, taking into account the impact of future evaporation and bathymetric changes, demonstrates an additional increase in reductions of water transfer of around 4%, which reveals the need to consider these effects in hydrological planning.

     

NeStRes – Model for Operation of Non-Strategic Reservoirs for Irrigation in Drylands: Model Description and Application to a Semiarid Basin

Water availability in dry inhabited environments has usually been promoted by large strategic reservoirs, but small non-strategic ones, built by farmers and communities, are unable to cope with long term droughts and inappropriate for human supply. Nevertheless, small reservoirs promote water spatial distribution and play a major role for livelihood in rural areas. To fill the gap of operation methods for non-strategic reservoirs used for irrigation where water is a limiting factor, the NeStRes model was developed. The model is composed of three modules: i) hydrological: to define the reliability of water withdrawals from the reservoir; ii) agricultural: to simulate crop production based on water availability; iii) economic: to compute the possible income from irrigated agricultural crops. NeStRes was applied to 91 reservoirs of the semiarid Banabuiú River Basin – BRB, Brazil. The simulations indicated that the maximum income from the cultivation of maize is obtained when the reservoirs are intensely used, drying completely in one to two thirds of the time. Adoption of a fixed reliability level of daily water supply (54%, in the BRB) generates at least 85% of the maximum possible income for all simulated reservoirs. This model application suggests a paradigm change in the operation of small non-strategic reservoirs in drylands: to use water for crop production and save the revenue, instead of saving water, which is susceptible to evaporation. Although high reliability level is desired for human supply by strategic reservoirs, non-strategic ones can be more intensely explored to generate income from irrigated agriculture in drylands.

     

Analysis of Virtual Irrigation Water. Application to Water Resources Management in a Mediterranean River Basin

Virtual water, understood as the volume of water needed to produce a good or service, in the context of trade among countries, allows assessing the relative dependency of different countries on imported virtual water. The assessment of virtual water flows in virtual water trade studies is generally carried out at the national level, thus concealing the spatial variability of many countries that comprise a wide range of agro-climatic areas. A finer spatial resolution is needed to apply the virtual water concept with a view to improving local water resources management at the regional or basin scale. This paper presents a more detailed analysis of blue agricultural virtual water at sub-basin scale, which is aggregated to the basin scale for the Guadalquivir River basin in southern Spain. Given that around 80% of the available blue water resources of this region are used in agriculture, improving irrigation water management is of great interest to the basin water resources management. The main objective of this paper is to estimate the virtual irrigation water balance; an important component of the agricultural water footprint that provides additional information to the basin blue water balance and contributes to achieving a more rational and efficient management of basin water resources. Management recommendations focusing on the spatial redistribution of irrigated crops according to both their water efficiency and productivity are proposed with the aim of saving blue water for other purposes such as drought mitigation or environmental flows, among others. In particular, the proposed measures affect irrigated olive trees; the most widespread irrigated crop in this basin.     

河北省水环境污染农业损失研究

在水环境污染损失研究已有理论的基础上,从水环境污染经济损失估算的实用性出发,针对河北省水环境污染对农业影响的现状和特点,首先对农业污灌进行了界定,然后对2000年─2004年采用污灌的农作物实际情况,采用市场价值法对水环境污染在农业上造成的损失进行了估算,并与当年农业经济总收入进行了对比,进而提出了改进水环境对农业污染现状的对策和建议。     

An Innovative Option Contract for Allocating Water in Inter-Basin Transfers: the Case of the Tagus-Segura Transfer in Spain

The Tagus-Segura Transfer (TST), the largest water infrastructure in Spain, connects the Tagus basin’s headwaters and the Segura basin, one of the most water-stressed areas in Europe. The need to increase the minimum environmental flows in the Tagus River and to meet new urban demands has lead to the redefinition of the TST’s management rules, what will cause a reduction of transferable volumes to the Segura basin. After evaluating the effects of this change in the whole Tagus-Segura system, focusing on the availability of irrigation water in the Segura, the environmental flows in the Tagus and the economic impacts on both basins; we propose an innovative two-tranche option contract that could reduce the negative impacts of the modification of the Transfer’s management rule, and represents an institutional innovation with respect to previous inter-basin water trading. We evaluate this contract with respect to spot and non-market scenarios. Results show that the proposed contract would reduce the impact of a change in the transfer’s management rule on water availability in the recipient area.     

The Transboundary Impacts of Trade Liberalization and Climate Change on the Nile Basin Economies and Water Resource Availability

A multi-country, multi-sector computable general equilibrium (CGE) model is used for the first time to evaluate the economic and water resource availability effects of trade liberalization (removal of import tariffs) and facilitation (reducing non-tariff barriers) under climate change in the Nile Basin. The analysis uses the GTAP 9 Database and the GTAP-W model that distinguishes between rainfed and irrigated agriculture and implements water as a factor of production directly substitutable in the production process of irrigated agriculture. A full trade liberalization and improved trade facilitation scenario is considered with and without climate change. The study reveals that trade liberalization and facilitation generates substantial economic benefits and enhances economic growth and welfare in the Nile basin. The effect of instituting a free trade policy on water savings is found to be limited, while climate change improves water supply and hence irrigation water use, enhancing economic growth and welfare in the basin.     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

Valorization of Irrigation Water in A Basin with Large Hydropower Production through Coupled Hydrological and Electric System Modelling

The problem of allocation of limited water resources for multiple and diverse activities with growing demand calls for the need to develop appropriate tools for water valorization. This work develops a methodology to estimate the economic value of water in a basin with large hydropower production and a growing demand for rice irrigation, based on a coupled hydrological and electric system modelling approach. Inflow deficits to the hydroelectric system induced by the irrigation reservoirs within the basin are simulated under different irrigation scenarios. The simulated inflow deficits are integrated to an existing model of the interconnected electric system to evaluate the associated increase in generation costs under different energy scenarios. The impact of inflow deficits in turbinated and spilled flow and generation costs are comprehensively explored. Both annual mean and interannual variability of overcosts increase with increasing irrigation demand. However, if normalized by yearly varying rice planted area, the distribution of additional costs does not change substantially. Moreover, the distribution of normalized overcosts per unit irrigated area is also invariant to energy scenarios, although the relative impact in total costs decreases as the proportion of hydroelectric generation diminishes.     

万家寨引黄供水区的农业灌溉问题分析

万家寨引黄工程主要为大同市、平朔区、太原市提供工业用水。对农业，计划将原被工业挤占的当地水资源量归还农业灌溉。本文通过分析三个供水区农田灌溉及当地水资源现状，以及对各供水区进行水量平衡分析和经济效益分析，论证了归还后所增加的农业灌溉水量的经济效益是显著的，该项农业供水计划是可行的。     

New water uses in the Segura basin: conflicts around gated communities in Murcia

The Segura basin in southeast Spain is characterised by massive over-use of its water resources. Groundwater resources are being depleted, desertification risk is high and the river ecosystem is near to collapse with merely 4% of its original runoff reaching the mouth. Meanwhile, the water cycle has been deeply technologized to meet the needs of an irrigated agriculture that has been growing since the beginning of the twentieth century. Today, the introduction of new water uses for the irrigation of green spaces in gated communities priding themselves on their first-class golf courses is putting further pressure on water resources. These developments are provoking conflicts between sections of society as well as between levels of state administration. This article investigates why reactions to gated communities are so different. To do so, an approach that highlights actors' differing perceptions of the state of Murcia's waterscape and subsequent attitudes towards water management is used.     

气象要素对水面蒸发量影响程度的灰色关联分析

根据新疆玛纳斯县气象站1996年至2003年小型蒸发皿蒸发量及相关常规气象观测资料,利用灰色关联度分析法分析了各气象要素对水面蒸发的影响程度,结果表明各气象要素对小型蒸发皿月平均水面蒸发量的影响程度从大到小的排列顺序均为气温、降水量、风速、日照时数。希望从气象因素的角度出发,为灌区内大中型平原水库的优化调度提供理论参考。     

Impact of the Syrian conflict on irrigated agriculture in the Orontes Basin

The impact of conflict on irrigated agriculture and consequently summer crop production within conflict-affected agricultural lands was observed in the Orontes Basin. Water and energy use were reconfigured through a transition from rainfed to irrigated agricultural production over the past 20 years, but have been disrupted as the Syrian war has unfolded since 2011. Remotely sensed vegetation indices were used to determine irrigated summer crop yields during the year 2013. Findings suggest that irrigated agricultural production dropped between 15% and 30% in the Syrian portion of the basin in 2000–2013, with hotspots identifiable in Idleb, Homs, Hama, Daraa and Aleppo. The developed approach demonstrated effectiveness in quantifying and geolocating hotspots where conflicts have the strongest impact on agricultural water use, agricultural production, and eventually support relief and regional agricultural reconstruction in this and other conflict regions.     

节水灌溉工程技术在杭埠河灌区的应用

杭埠河灌区因地制宜,采用多种节水灌溉工程措施,解决了灌区水资源紧缺问题,为灌溉农业的发展创造了条件,保障了灌区的农业发展。     

井灌类型区农业高效用水模式及产业化示范

农业高效用水管理示范工程是国家科技部在“九五”期间批准立项的重大科技产业工程项目。井灌类型区农业是我国重要的灌溉农业类型区一，提高井灌区的灌溉水利用率和单方水的生产效率，对节约用水，提高农业生产水平具有重要的意义。河北省三河市通过提高井灌区水的利用率，创建和发展了相关产业，使该项目成为农业高效用水科技产业示范工程。     

动水水面蒸发实验研究初探

黄河是一条多泥沙河流。以往在计算黄河河道和水库水面蒸发时，都是根据陆地蒸发器观测的清水静水水面蒸发一计算的。这样计算是否会产生较大的误差，一直是大家关心的问题。目前有关动水水面蒸发的研究还很少。我们于１９９５年７－１０月在巴彦高勒蒸发实验站进行了清水，浑水动水蒸发实验。     

Rational Pricing of Water as an Instrument of Improving Water Use Efficiency in the Agricultural Sector: A Case Study in Gujarat,India

The agricultural sector in India accounts for over 85% of the total water used for various purposes in the country. However, the efficiency of water use in agriculture is very low, approximately 40% for surface irrigation and 60% for groundwater irrigation. Part of the reason for the low efficiency is the highly subsidized price of irrigation water that encourages the excessive application of water to crops. This paper is based on a case study conducted in the command area of a public irrigation canal in the state of Gujarat, India. It attempts to explore the role of the rational pricing of canal irrigation water in motivating farmers to use water judiciously and thereby enhance the water use efficiency in irrigated agriculture. The paper contends that farmers are sensitive to an increase in irrigation water charges, but unless the administered price is increased to the level that would prevail in a free market, it will not have its intended effect on irrigators.     

苏北地区灌溉农业水质监测分析

为掌握农业灌溉过程中水环境的变化情况,对苏北地区地表水、地下水水质进行了连续五年监测。结果表明:地表灌溉水、地下灌溉水水质综合污染指数均小于1,但有升高的趋势;灌溉退水中部分污染物浓度较灌溉水上升,个别单项指标超标,但不构成综合污染。提出解决制约农业可持续发展重要因素———灌溉农业用水问题的几点建议。     

基于模糊集对分析的灌区水库旱限水位及供水策略优化研究

随着经济社会发展和气候条件改变,我国区域干旱问题日益突出,水库在抗旱减灾过程中的作用越来越凸显,旱限水位的提出与应用对有效发挥大中型水库在抗旱中的调控作用、缓解流域旱情具有重要意义。针对旱限水位研究现状,本文以史河灌区梅山水库为例,首先考虑城乡供水、农业灌溉、水力发电和生态环境等诸多因素,构建基于模糊集对分析法的水库灌区水资源系统运行效果综合评价模型,并以水资源系统综合运行等级最优为目标,以分期分级旱限水位、灌溉限供措施（基于水库来水特征和作物生长特性）为优化变量,运用免疫遗传算法进行系统优化求解,最后对比有无旱限水位下水库水资源系统综合运行效果,并分析了不同控制方式下水库供水变化和灌区作物因旱减产风险。结果显示：该优化方法相较于以水库供水经济效益为目标旱限水位确定方法,多项年均指标都有较大改善,其中梅山水库经济效益提高了46万元,充反调节水库水量增加了555万m³,而水库弃水量减少了566万m³;史河灌区塘坝供水量增加了253万m³,而作物减产率下降了3.32%,同时作物因旱减产风险降低了3.15%。可见,运用系统综合评估决策方法有利于改善水库灌区系统综合运行效果,提高系统水资源利用效率和水库灌区经济效益;优化的旱限水位控制和与作物生长特性相适应的优化供水策略相对于经验性控制能有效减少灌区中稻因旱减产率,为保障旱限水位的顺利实施和干旱时期农业灌溉抗旱提供有力支撑。     

Effect of Drip Irrigation with Saline Water on Water Use Efficiency and Quality of Watermelons

High ground water salinity, high water table and secondary soil salinization are dominant in the Hetao Region, China. For the purposes of eliminating secondary salinity and enhancing water use efficiency, drip irrigation of watermelons with saline water was conducted in order to reduce ground water level and soil salinization. Saline groundwater, ranging in salinity from 3.3 dS m^-1 in the early season to 6.3 dS m^-1 at the harvest time was used. Four irrigation treatments (control, 30, 60, and 90% of evaporation from Chinese Evaporation Pan) were used in the experiments.The control treatment was not irrigated through out the season, as is the local practice. The yield of watermelons was increased and the quality improved under drip irrigation, as compared with control, with the highest increases in both yield and quality in the 60% treatment. The water use efficiency as determined by lysimeter measurements for different treatments had the same trend. The water-product efficiency in the four treatments were 39.2, 30.7, 21.45, and 14.3 kg m^-3, respectively. Salts accumulated in the topsoil layer close to the emitter in the 30% treatment. Most salts were leached out of the root zone in the 60 and 90% treatments. The results suggested thatdrip irrigation of watermelon with saline water was feasible.