The Economic Impact of Water Evaporation Losses from Water Reservoirs in the Segura Basin,SE Spain

In this paper we assess the economic impact of evaporation losses from great dams (GDs) and on-farm agricultural water reservoirs (AWRs) in the semi-arid Segura River basin, SE Spain. Evaporation losses from water reservoirs reduce the high water use efficiency reached in agriculture by means of other techniques such as well-built water pipes or drip irrigation and have a substantial economic impact. Evaporation losses have been calculated using Class-A pan evaporation data and pan coefficients, whereas their economic impact has been assessed using an economic mathematical programming model that simulates land and water allocation in the different irrigated areas of the basin. Our results show that annual evaporation from GDs and AWRs represents 8.7% of the water currently available for irrigation in the Segura basin. The economic impact of such losses has been estimated in a reduction of 6.3% of the value of agricultural production and 5.4% of the farm net margin. As less water is effectively available for farmers the basin’s irrigated area is reduced in a 7.5%. This impact is greater, in both absolute and relative terms, in the areas accommodating the most intensive and profitable irrigated agriculture. The applied methodology and results could be useful to regional water agencies and collective irrigation schemes for future planning and management, including the assessment of alternatives for reducing evaporation from reservoirs.     

Simulation-Optimization Modeling for Conjunctive Use Management under Hydrological Uncertainty

The canal water supply, which is the only source of irrigation, in the rice-dominated cropping system of the Hirakud canal command (eastern India) is able to meet only 54 % of the irrigation demand at 90 % probability of exceedance. Hence, considering groundwater as the supplemental source of irrigation, conjunctive use management study by combined simulation-optimization modelling was undertaken in order to predict the maximum permissible groundwater pumpage from the command area. Further, optimal land and water resources allocation model was developed to determine the optimal cropping pattern for maximizing net annual return. The modelling results suggested that 2.0 and 2.3 million m³ of groundwater can be pumped from the bottom aquifer during monsoon and non-monsoon seasons, respectively, at 90 % probability of exceedance of rainfall and canal water availability (PERC). Optimal cropping patterns and pumping strategies can lead to about 51.3–12.5 % increase in net annual return from the area at 10–90 % PERC. The sensitivity analysis of the model indicates that the variation in the market price of crops has very high influence on the optimal solution followed by the cost of cultivation and cultivable area. Finally, different future scenarios of land and water use were formulated for the command area. The adoption of optimal cropping patterns and optimal pumping strategies is strongly recommended for sustainable management of available land and water resources of the canal command under hydrological uncertainties.     

Development and application of a simulation model for reservoir management

The success of irrigation system operation and planning depends on accurate quantification of supply and demand, and an equitable distribution of available water. The ultimate aim of this study was to determine how to meet the irrigation water demands if possible or to minimize the gap between the water supply and the demand. Most of the irrigation literature focuses only on the demand and the distribution aspects of this issue Irrigation projects that receive water from reservoirs, however, can be challenging to manage because the annual fluctuations in available water release from a reservoir can have a considerable impact on the irrigation management strategy. In real‐world situations, the reservoir operating rules guide reservoir operators in making actual water release decisions. This study develops a water balance simulation model for reservoir management, as well as testing it for Kangsabati Reservoir, West Bengal, India. Two rule curves for deciding irrigation water available from the reservoir were generated by taking the average and minimum stage values on a daily basis for a 16‐year period (1988–2003). Maintaining a minimum stage of 120.4 m throughout the year served as another rule to decide the release water available for irrigation. The minimum allowable stage of reservoir corresponding to a particular date of the year can be determined from those reservoir specific rule curves generated for irrigation purposes. The maximum permissible water release/outflow for irrigation from the test reservoir was taken as the volume of water available above the minimum allowable stage corresponding to the selected rule curve. The saturated hydraulic conductivity value (K_S) was calibrated to be 4.31 mm day^?1 for Kangsabati Reservoir.     

Variation and Trends in Agricultural Drainage Water Reuse in Egypt

ABSTRACT

A substantial quantity of agricultural drainage water flows annually from the Nile Delta to the Mediterranean Sea and North Lakes. The volume and salinity of this water vary both with time and space. Policies for developing water resources in Egypt and maximizing its use include the reuse of agricultural drainage water for irrigation. This implies that water of lower quality than the Nile water will be used in irrigation. The reuse of this water as a reliable resource is limited by its quality, which in turn determines the quantity that can be used.

During the past decade Egypt started an ambitious program towards the goal of achieving higher water use efficiency to face the increasing water demands. The future improvement of the irrigation system, the better allocation of available water resources and the efficient utilization of irrigation water will affect the quantity and quality of agricultural drainage water: The start of this program was associated with a sharp decrease in the natural flow of the River Nile. The prevailing operational and management conditions had decreased the irrigation and drainage discharges and increased the salinity of drainage water

In this paper the historical discharge and salinity data about the drainage water in the Nile Delta will be analyzed to determine the trends and tendencies of their changes. The effect of management of Nile water releases from the High Aswan Dam on drainage water quantities and qualities is discussed. This study is carried out on a regional scale, covering the east, the middle and the west parts of the Delta.     

Changes in Irrigation Planning and Development Parameters Due to Climate Change

Considering changes in irrigation planning and development due to climate change is necessary to avoid system failure. This study demonstrated that changes in dependable flow and diversion water requirements in the future due to climate change will reduce potential irrigable areas. Climate change were based on the published projected climate in the study area. The dependable flow derived from successfully calibrated and validated Soil and Water Assessment Tool (SWAT) model streamflow simulations and the diversion water requirements based on the CROPWAT estimations of irrigation scheme were used to assess the potential irrigable areas. Substantial reductions in potential rice production areas (-4% to – 39%) were largely due to dwindled dependable flow (-1% to -25%) and an increase in diversion water requirement (+?7% to?+?26%). Reduction in potential irrigable area was projected during dry and normal years and may worsen towards the late twenty-first century under the worst-case climate scenario. Swelling of rivers during wet years will increase stream flows and potential irrigable areas but may also pose a danger of flooding. The development of water storage structures is necessary to reduce the adverse impacts of too much water during the wet years. Crop calendars should also be retrofitted to optimize the use of available rainfall during dry and normal years and climate-proof future irrigation systems. The results showed that it is necessary to incorporate climate change in irrigation planning and development. The methodologies described here could be used to climate-proof future irrigation systems in other areas in the Philippines and other countries.

     

山口岩水库水温计算及其对下游河道水温影响分析

对山口岩水库水温分布、水库泄水温度状况及坝下游河道水温沿程变化作了预测,结合灌区工程布置及灌溉农田的基本情况,对水库兴建后水温对下游农田灌溉的影响进行分析评价,结果表明:库区水温结构属典型的分层型;在坝址至半山水汇入口6km长的河段水温回升较慢,年平均水温温升率为0 414℃/km,对应的左岸直灌区和锡陂灌区沿程水温在水稻生育期的月平均值低于水稻生长所需的最低水温,需采取调温措施;在坝址下游10km断面,由于受袁河支流半山水汇入影响,各月平均水温与建库前天然水温相差不超过0 3℃,能满足农田灌溉的要求。最后从工程设计、水库调度运行、灌溉方式等方面提出了对策措施。     

汾河二坝灌区引洪灌溉分析

本文对汾河二坝灌区作物生长缺水现状和二坝水文站以上可利用的洪水资源进行了统计。认为二坝以上每年来洪是解决灌区农作物受旱的水源之一。调查分析了灌区历年来的引洪量、引洪特点、经验和教训。对今后引洪中可能存在的问题及其它工程进行了分析并提出了建议。     

水足迹框架下稻田水资源利用效率综合评价

为综合评价稻田水资源利用效率,优选高效灌排模式,本文基于水足迹理论,考虑水资源利用率、水资源产出效益和水量及环境效益3个方面,构建稻田水资源利用效率综合评价指标体系,利用层次分析法和模糊综合评价模型对2015—2018年各处理稻田水资源利用效率进行综合评价,并与单个指标的评价进行对比。结果显示：各处理作物水足迹年均值分别为976.8（浅水勤灌）、1008.7（浅湿灌溉）、954.4（控制灌溉）和792.6 mm（蓄水-控灌）,蓝、绿及灰水比例年均值分别为16.4%、40.9%和42.7%;水资源产出效益在水资源利用效率评价中占据首要位置;各处理稻田水资源利效率综合评分值在2.8058~3.9432之间,等级为中或中高,优选出的高效灌排模式为蓄水控灌;作物水分利用效率、作物水足迹与综合评价的对比表明水资源利用效率综合评价至关重要。基于水足迹的稻田水资源利用效率评价能够为农业用水效率评价提供一种新视角,为农业节水尤其是水稻节水的科学研究和决策提供实践依据。     

The water reclamation and reuse project of El Prat de Llobregat, Barcelona, Spain.

Water reclamation and reuse have become essential components of water resources management in the Metropolitan Area of Barcelona, by helping to develop additional water resources in the lower Llobregat River, one of its main sources of water supply. By generating a reliable flow of 300,000 m3/day of high quality reclaimed water, the options available for integrated water resources management have widely expanded to allow in-stream river water substitution, restoration of natural wetland areas, agricultural irrigation, and supply to a seawater intrusion barrier. Those management options have been possible thanks to the implementation of an extensive water distribution system that allows distribution of reclaimed water to a point 15 km upstream of the reclamation facility, and to a seawater intrusion barrier within a few kilometres of the plant. The cost of producing reclaimed water using a physico-chemical process (0.05 euro/m3) and the investment required for such a facility (0.21 euro/m3 annual capacity) are very close to those of similar large scale projects in Spain. However, higher degrees of treatment, such as demineralization for agricultural irrigation and for injection into a seawater intrusion barrier, result in considerable increases of both water reclamation cost and investment costs.     

气候变化影响下的赣江流域水资源变化趋势与幅度分析

利用全球气候模式输出结果,经统计降尺度模型降解后得到流域尺度的降水和气温要素,根据实测资料建立气温—蒸发回归关系以及新安江水文模型,使用耦合模拟和MK趋势分析评估未来气候变化情景下赣江流域水资源量的变化趋势和幅度。研究结果表明:未来不同排放情景下的年降水量、年蒸发量和年径流量等水文气候要素变化趋势以显著增加为主。未来年降水量、年蒸发量和年径流量的多年平均值相对基准期有较小幅度增加,最大增幅为年径流量的13.81%。降水、蒸发和径流的年内变化有明显的季节性特征,汛期径流增加、非汛期径流减少的不均匀情况加剧,在一定程度上可能增加赣江流域未来的防洪压力和枯水期供水压力。     

Water Management of Irrigation Dams Considering Climate Variation: Case Study of Zayandeh-rud Reservoir, Iran

Dependency of reservoir operation on the climate variation occurs especially in regions, where agricultural demand has a significant share of the total water demands. The variability between demands that are based on annual climate conditions may be larger than the uncertainty associated with other explanatory variables in long-term operation of an irrigation dam. This paper proposed a rule curves to the water managers of the Zayandeh-rud reservoir in Iran in long-lead reservoir operation. A regional optimal allocation of water among different crops and irrigation units is developed. The optimal allocation model is coupled with a reservoir operating model, which is developed based on the certain hedging that deals with the available water and the water demands mutually. This coupled model is able to activate restrictions on allocating water to agricultural demands considering variation of inflow to the reservoir, variation of demands and the economic value of allocating water among different crops and irrigation units. The resulted rule curve is presented with a number of tables for more details and accuracy and a simple curve, which is more useful for operational purpose.     

旱涝交替下驮英灌区年内水资源优化调控研究

针对旱涝频发下区域水资源分配不均问题,基于某时段可供水量是否满足用户层理想需水量,提出旱涝交替下年内水资源优化调控方法。以驮英灌区为研究对象,建立水资源优化调控模型,通过2030规划水平年驮英灌区供水侧供水能力分析及需水侧水资源需求预测,分析远期水资源供需平衡情况,研究年内尺度的水资源优化调控方案。结果表明,规划水平年总缺水1 692万m³,年缺水率较调控前降低37.7%,生活用水得到充分保证,有效缓解了水资源短缺和分配不均局面。研究成果可为驮英灌区旱涝交替水资源优化调控提供决策方案,且该方法可供旱涝频发区域水资源优化调控参考。     

现代灌溉水肥调控原理与技术研究进展

我国一般年份农业缺水约300亿m3,农业水肥利用率主要指标相当于国际先进水平的60％～70％,农业缺水和面源污染问题日益突出,严重影响国家粮食安全和生态安全.本文综述了创新团队在现代灌溉水肥调控原理、技术与模式等方面所开展的研究工作进展.通过多年的研究,发展了现代灌溉施肥变量调控理论方法,提出了精量滴灌水肥高效调控技术...     

The future sustainability of water supply in Kuwait

Abstract

The main natural source of water available in Kuwait is the brackish groundwater located in the Kuwait Group and the Dammam aquifers, where the salinity ranges from 4300 to 10200 mg/l and from 2500 to 10000 mg/l, respectively. Limited fresh groundwater resources in Al‐Rawdhatain and Umm Al‐Aish fields, which have a salinity of 359 ‐1737 mg/l, are also available. Most of the groundwater in Kuwait is used for irrigation, domestic purposes, small‐scale industries and for blending with distilled water. Because rainfall is seasonal and less than annual evaporation, the recharge of the groundwater from rainfall is negligible. The objective of this paper is to assess the different water resources in Kuwait in order to make an integrated management plan and to focus on future sustainability. Generally, in the State of Kuwait, there is increasing pressure on the natural water resources because of the exploitation of the aquifers at a rate exceeding that of both the groundwater recharge and population growth (from 1.4 million in 1980 to 2.55 million in 2003). This has lead to the observed decline in groundwater level and to the deterioration of water quality. In the early 1950s, a plan was endorsed in Kuwait to establish seawater desalination plants. By 2005, six desalination plants have been established, with a total capacity of distillation units of 1434.72 ×103 m³/d (315.6 MIGD). However, the gross maximum consumption for the year 2003 reached a value of 1440.17 ×103 m³/d (316.8 MIGD), which is higher than the total capacity of the available distillation units. Given the limitation of conventional water and the shortages of non‐conventional water, along with the increasing population, Kuwait must consider the recycling of wastewater for irrigation, industrial or any other unrestricted non‐potable purpose.     

SIMETAW# - a Model for Agricultural Water Demand Planning

A successful water management scheme for irrigated crops requires an integrated approach, which accounts for water, soil, and crop management. SIMETAW# is a user friendly soil water balance model that assesses crop water use, irrigation requirements, and generates hypothetical irrigation schedules for a wide range of crops experiencing full or deficit irrigation. SIMETAW# calculates reference evapotranspiration (ET_o), and it computes potential crop evapotranspiration (ET_c), and the evapotranspiration of applied water (ET_aw), which is the amount of irrigation water needed to match losses from the effective soil root zone due to ET_c that are not replaced by precipitation and other sources. Using input information on crop and soil characteristics and the distribution uniformity of infiltrated irrigation applications in full or deficit conditions, the model estimates the mean depth of infiltrated water (IW) into each quarter of the field. The impact of deficit irrigation on the actual crop evapotranspiration (ET_a) is computed separately for each of the four quarters of the cropped field. SIMETAW# simulation adjusts ET_o estimates for projected future CO₂ concentration, and hence the model can assess climate change impacts on future irrigation demand allowing the user to propose adaptation strategies that potentially lead to a more sustainable water use. This paper discusses the SIMETAW# model and evaluates its performance on estimating ET_c, ET_a, and ET_aw for three case studies.     

Using SWAT for Strategic Planning of Basin Scale Irrigation Control Policies: a Case Study from a Humid Region in Northern Germany

The eco-hydrological model SWAT is used worldwide for simulating hydrology and water quality of agricultural catchments. One of the main water uses is irrigation, predominantly in arid and semi-arid regions. Climate impact simulations show that a future increase of irrigation demand can be expected for humid regions. Options for adaptation include the improvement of irrigation techniques and the modification of crop patterns. In our study we investigate the application of SWAT for the development of water saving irrigation control strategies in a humid river catchment in Northern Germany. We developed different scenarios using both soil moisture deficit control and plant water demand control. The results show plausible changes of irrigation amounts when changing the trigger points of both control methods. By deficit control strategies, the water consumption could be reduced with only a moderate decrease of crop yield. Differences between soil characteristics were well shown in the SWAT simulations, but the model consistently overestimated irrigation values. Furthermore we found a high variability of the model errors between the different years, even if the long term average values are considered acceptable. Future research is needed to improve the model accuracy in automatic irrigation control.

     

充分灌与调亏灌溉条件下桃树滴灌的耗水量研究

本文研究了充分灌与调亏灌溉条件下桃树滴灌的耗水量。在田间设置有两个处理，其一是在整个生育期以蒸发量的80%进行充分灌溉；其二是在果实生长缓慢期以蒸发量的20%进行亏缺灌溉，而在其它季节以蒸发量的80%进行充分灌溉。利用石膏块土壤水分传感器和中子仪分别测量了根区土壤水势和土壤含水量的变化，并实测了果实生长量、枝条生长量和产量。利用水量平衡法得出了在上述两种滴灌条件下桃树不同生育期的日均耗水量与蒸发皿系数。与充分灌比较，调亏灌溉对产量没有影响，灌水量减少了32%，并有效抑制了枝条生长。     

Investment in Irrigation Systems under Precipitation Uncertainty

Efficient agricultural water management is indispensable in meeting future food demands. The European Water Framework Directive promotes several measures such as the adoption of adequate water pricing mechanisms or the promotion of water-saving irrigation technologies. We apply a stochastic dynamic programming model (SDPM) to analyze a farmer??s optimal investment strategy to adopt a water-efficient drip irrigation system or a sprinkler irrigation system under uncertainty about future production conditions, i.e. about future precipitation patterns. We assess the optimal timing to invest into either irrigation system in the planning period 2010 to 2040. We then investigate how alternative policies, (a) irrigation water pricing, and (b) equipment subsidies for drip irrigation, affect the investment strategy. We perform the analysis for the semi-arid agricultural production region Marchfeld in Austria, and use data from the bio-physical process simulation model EPIC (Environmental Policy Integrated Climate) which takes into account site and management related characteristics as well as weather parameters from a statistical climate change model. We find that investment in drip irrigation is unlikely unless subsidies for equipment cost are granted. Also water prices do not increase the probability to adopt a drip irrigation system, but rather delay the timing to invest into either irrigation system.     

Simple Myths and Basic Maths About Greening Irrigation

Greening the economy is mostly about improving water governance and not only about putting the existing resource saving technical alternatives into practice. Focusing on the second and forgetting the first risks finishing with a highly efficient use of water services at the level of each individual user but with an unsustainable amount of water use for the entire economy. This might be happening already in many places with the modernization of irrigated agriculture, the world’s largest water user and the one offering the most promising water saving opportunities. In spite of high expectations, modern irrigation techniques seem not to be contributing to reduce water scarcity and increase drought resiliency. In fact, according to the little evidence available, in some areas they are resulting in higher water use. Building on basic economic principles this study aims to show the conditions under which this apparently paradoxical outcome, known as the Jevons’ Paradox, might appear. This basic model is expected to serve as guidance for assessing the actual outcomes of increasing irrigation efficiency and to discuss the changes in water governance that would be required for this to make a real contribution to sustainable water management.     

Multivariate Bayesian Regression Approach to Forecast Releases from a System of Multiple Reservoirs

This research presents a model that simultaneously forecasts required water releases 1 and 2 days ahead from two reservoirs that are in series. In practice, multiple reservoir system operation is a difficult process that involves many decisions for real-time water resources management. The operator of the reservoirs has to release water from more than one reservoir taking into consideration different water requirements (irrigation, environmental issues, hydropower, recreation, etc.) in a timely manner. A model that forecasts the required real-time releases in advance from a multiple reservoir system could be an important tool to allow the operator of the reservoir system to make better-informed decisions for releases needed downstream. The model is developed in the form of a multivariate relevance vector machine (MVRVM) that is based on a sparse Bayesian regression model approach. With this Bayesian approach, a predictive confidence interval is obtained from the model that captures the uncertainty of both the model and the data. The model is applied to the multiple reservoir system located in the Lower Sevier River Basin near Delta, Utah. The results show that the model learns the input–output patterns with high accuracy. Computing multiple-time-ahead predictions in real-time would require a model which guarantees not only good prediction accuracy but also robustness with respect to future changes in the nature of the inputs data. A bootstrap analysis is used to guarantee good generalization ability and robustness of the MVRVM. Test results demonstrate good performance of predictions and statistics that indicate robust model generalization abilities. The MVRVM is compared in terms of performance and robustness with another multiple output model such as Artificial Neural Network (ANN).