Remote Sensing and Economic Indicators for Supporting Water Resources Management Decisions

This paper demonstrates that combining spatial land surface data with socio-economic analysis provides a number of indicators to strengthen decision making in integrated water and environmental management. It provides a basis to: track current water consumption in the Inkomati Basin in South-Africa; adjust irrigation water management; select crop types; facilitate planning; estimate crop yields before harvesting, and consequently to forecast market price development. Remote sensing data and economic analysis can also be used to study the spatial distribution of water consumption as an indicator of equity in access to water resources. It even enables identification of farms that consume more irrigation water than formally allocated. Finally, it provides a basis to assess the cost-effectiveness of various ways to reduce agricultural water consumption. So, this approach is potentially useful for determining water consumption, refining water allocation policies, and determining the potential for water transfers through mechanisms such as water trading.     

鲁北地区秸杆覆盖对冬小麦需水量、作物系数及水分利用效率的影响

作物系数和需水量是制定作物灌溉制度和计算区域水资源平衡的重要参数,不同气候和不同栽培条件下作物系数和需水量会发生变化。通过大田试验,以Penman-Monteith公式计算小麦播种~成熟期间参照作物蒸散量,并利用农田水量平衡方程及土壤水分胁迫系数计算作物实际蒸发蒸散量,进而对小麦秸杆覆盖和露地栽培条件下各生育阶段的作物系数进行计算。结果表明,鲁北地区小麦秸杆覆盖栽培比露地栽培生育期内作物需水量减少40.3 mm,作物系数降低9.1%,水分利用效率增加18.0%。冬小麦产量提高10%左右。     

Evaluating the Performance of Agricultural Water Distribution Systems Using FIS,ANN and ANFIS Intelligent Models

Increasing water use efficiency in the agricultural sector requires the use of appropriate methods for intelligent performance evaluation of surface water distribution systems in agriculture. Therefore, in this study a systematic approach was developed for operational performance appraisal of the agricultural water distribution systems. For this purpose, Fuzzy Inference System (FIS), Artificial Neural Network (ANN), and Adaptive Neuro-Fuzzy Inference System (ANFIS) were used to evaluate the technical performance of irrigation network, considering the uncertainties in the water exploitation process. The performance of the developed models was studied on the Roodasht irrigation canal, located in central Iran, which suffers from severe fluctuations in the inflow, by evaluating the adequacy, efficiency, and equity of surface water distribution. Hydraulic simulation of water distribution system, as well as providing the information required for training and validation of the intelligent models, were performed using the HEC-RAS model. The results showed that compared to the FIS model, ANN and ANFIS models similarly predicted the model outputs with lower errors at almost the same level. The adequacy, efficiency, and equity indicators were predicted by ANFIS model with MAPE of 0.16, 0.01 and 0.23, respectively. Also, FIS model was only able to predict the efficiency and could not predict the adequacy and equity with appropriate performance. The findings of this study reveal that since the ANFIS model uses both FIS and ANN models in its structure, it considers the model uncertainty reliably, and it can be used to evaluate the performance of agricultural water systems.

     

Equity in bulk water allocation: the case of the Mahaweli Ganga Development Project in Sri Lanka

This article evaluates the equity performance of bulk water allocation as an irrigation management strategy in the Mahaweli Ganga Development Project, Sri Lanka. Through semi-structured interviews with farmers and irrigation officials, the study collected local perceptions using seven indicators: water rights; decision-making process; contribution of resources for irrigation maintenance; water allocation rules; actual water distribution; information sharing; and conflict resolution. The results highlight gaps in the institution such as the need to enhance the water rights of landless farmers, further encourage crop diversification, increase transparency in decision making, instil a risk-management approach, and strengthen accountability.     

Relating Crop Water Consumption to Irrigation Water Supply by Remote Sensing

A new set of irrigation performance indicators based on remote-sensing estimates of evapotranspiration is introduced. These evapotranspiration indicators are the relative evapotranspiration or crop stress and the water efficiency as well as their uniformity. With a remote-sensing evapotranspiration algorithm (SEBAL) maps of actual crop water consumption are derived. These maps are one of the inputs in the evapotranspiration indicators, together with GIS data (digitized irrigation unit boundaries) and field data (irrigation delivery schedule and water flow). This approach is applied on the Rio Tunuyan irrigation scheme, Mendoza, Argentina, which is served by surface water and privately owned ground water pumps. A homogeneous pattern of actual crop water consumption is detected from the highest irrigation level till the lowest (farm) level (coefficient of variance from 8.6% to 6.1% and 14.0% of secondary, tertiary and pixel level, respectively). Considering that a rotational irrigation schedule at tertiary and farm level is present, the results indicate that ground water supply through extraction and capillary rise equalize the spatial patterns in crop water consumption. The latter is proved by a comparison between (i) the areal water consumption from remote-sensing measurements, (ii) the areal water supply and (iii) additional field information on ground water extraction and capillary rise.     

Remote Sensing and Hydrological Measurements for Irrigation Performance Assessments in a Water User Association in the Lower Amu Darya River Basin

Irrigation water management in Central Asia is notorious for its inefficiency. We assessed the operational performance of the irrigation scheme in one Water Users Association (WUA), Shomakhulum, in Khorezm district, Uzbekistan, in 2007 to provide recommendations for strategic water management planning. Relative evapotranspiration (RET), delivery performance ratio (DPR), drainage ratio (DR), depleted fraction (DF), overall consumed ratio (OCR), field application ratio (FAR) and conveyance ratio (CR) were used as performance indicators. The components of the water balance were obtained through remote sensing techniques and hydrological field measurements. The surface energy balance algorithm for land (SEBAL) was applied to MODIS satellite data to derive actual and potential evapotranspiration. Inflows and outflows were quantified with field measurements in the irrigation and drainage network using discharge rating curves. Ponding experiments allowed determining canal seepage losses. Water balances at field level were established for application efficiency estimations. The indicator values were then compared to efficiency target values taken from the literature in order to assess the operational capabilities of the irrigation scheme. The general performance of the irrigation scheme is very poor. DPRs exceeding 1.0 indicate that more water is delivered to the system than is demanded. The seasonal DF of 0.4 is lower than the target value of 0.6. Losses during the field application averaged at 57%, which is 24% above target values. Seasonal DR, OCR, CR and RET are 0.55, 0.51, 0.76 and 0.82 against the target values of 0.1, 0.54, 0.84 and 0.75, respectively. We conclude that the distribution mechanism can be considerably improved. Besides improving water distribution (timing and equity) in the network, another recommended intervention would be to increase the DF, particularly by interventions at field level that raise the FAR, which in turn will improve DR and OCR. This can be achieved by introducing modern water management approaches such as laser leveling, double-sided irrigation, and control of inflow through flow-measuring devices installed at farm gates, and adequate water pricing.     

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.     

Irrigation system performance and its impact on crop productivity in Sri Lanka

This article analyses the performance of two irrigation systems in Sri Lanka, using performance measures adapted from Theil's mean‐square forecast error concept. The performance is measured in terms of defined objectives that are decomposed into three components measuring adequacy, equity or dependability of water deliveries, and management capability. The relationship between the level of performance, as estimated by the above measures, and crop productivity is determined using regression analysis. The study demonstrates that input and institutional variables such as fertilizer, labour and power concentration have a positive impact on yields while poor irrigation management performance has a negative effect.     

Effect of Various On-Farm Water Management Scenarios on Equity and Productivity in Irrigation Networks

This research investigated the optimum on-farm water management methods for a summer crop (Maize). Water equity and productivity were optimized simultaneously by using genetic algorithms in Doroodzan Irrigation Network. Increase in water reduction fraction (WRF) (0.0 to 0.8) has the incremental effect on water equity (on average 19.4 %), however by increasing WRF, water productivity initially increased (on average 25.3 % at WRF?=?0.4) and then decreased. With increasing irrigation application efficiency (E_a) (40 to 90 %), the values of water equity and productivity increased by on average 52.8 and 91.5 %, respectively. Increment of conveyance efficiency of channels (E_c) (70 to 90 %) resulted in minimum incremental effect on water equity and productivity (on average 18.5 and 11.9 %, respectively). Furthermore, the values of performance measure decreased from wet water year to drought water year. Tape irrigation system was considered as the best choice at low quantities of WRF (<=0.4), however for higher values of WRF (>?=?0.6), sprinkler irrigation system was considered as the best choice for achieving higher values of water equity and productivity. Meanwhile, when equity and productivity were considered together for a specific method of deficit irrigation scheduling, under specified quantity of irrigation water, with increasing equity the water productivity reduction was negligible.     

Performance Assessment of a Water Delivery Canal to Improve Agricultural Water Distribution

The performance of an irrigation water delivery canal located in northern Iran, which supplies water to 5,514 ha of paddy fields through ten secondary canals, was investigated. Throughout the rice growing season in the region, two performance measures, the measure of adequacy (P_A) and the measure of equity (P_E), were calculated for the system. It was observed that the canal, in its current physical and operational condition, is unable to distribute available water among all upstream and downstream users adequately. While 46.7?% of the total area is experiencing significant water scarcity, the amount of water received by 51.4?% of the area is approximately three times more than required. To improve the performance of the canal, structural and non-structural modifications were proposed and assessed using the SOBEK hydrodynamic model. The results showed that implementing the proposed modifications would decrease the measure of equity by 71.7?%, meaning that the overall performance of the canal could be reasonably improved.

     

基于需水和输配水模拟与节水多准则分析的DSS模型应用研究

应用具有决策支持系统(DSS)功能的SEDAM模型模拟黄河上游惠农引黄灌区的灌溉需求与渠系输配水状况，利用节水多准则分析方法评价农田与输配水系统的改善方案。以田间实测的各类典型数据资料为基础，采用随机方法生成与田间和各级渠道相关的数据，产生用于多准则分析的属性数据和性能指标。根据不同水平的与农田及输配水系统相关的决策变量，设计了8种用于改善农田与输配水系统的模拟方案，通过模拟的需水量与现状供水量之间的对比以及模拟的各类效用值随时间变化的趋势，对模拟结果进行分析。结果表明，采用改善的农田与输配水系统运行方案可有效地减少惠农灌区的灌溉弃水和渠系输水渗漏量，较好地控制田间深层渗漏与地表径流损失，达到节水增产、改善农田生态环境的目的。     

Water Balance Study and Irrigation Strategies for Sustainable Management of a Tropical Ethiopian Lake: A Case Study of Lake Alemaya

Lake Alemaya in the Ethiopian Highlands has historically provided the surrounding area with water for domestic use, irrigation, and livestock and has served as a local fishery tank. Increasing irrigation and domestic water use, change in the local climate and changes in the surrounding land cover are believed to be the causes of Lake Alemaya’s demise. Expansion of major irrigated crops in particular chat (Catha Edulis), potato and vegetables and non-judicious use of irrigation water in the Lake Alemaya watershed led to presumption that irrigation is partly responsible for the withdrawal of large quantity of water from the lake. Thus, water balance study of Lake Alemaya was carried out under presumed scenarios in order to study the possible trends and fluctuations of the lake water level in response to proposed scenarios. Further, it is essential to study the irrigation performance for developing optimal irrigation schedules in the study area to make the best use of available water for long term sustainability of the water resources of Lake Alemaya. It was identified that expansion of the irrigated area in general and chat cultivation in particular in the study area have been the key to sustainable management of lake water, hence its expansion during the past 37 years (1965–2002) was studied through interpretation of satellite data. Subsequently, performance evaluation of the small-scale irrigation practices for major irrigated crops was carried out. Optimal irrigation schedules for different crop seasons were also developed for these irrigated crops using CROPWAT software. It was found that chat area increased from 190 ha in 1996 to nearly 330 ha in 2002. Further, it was observed that 43% surface area of the lake has reduced within a span of 37 years. Overall, maximum irrigation intensity of chat, potato and vegetables is observed during the first irrigation season of the crop calendar. Particularly, in case of chat, irrigation performance indicators such as Relative Water Supply (RWS), Relative Irrigation Supply (RIS), Depleted Fraction (DF) and Overall Consumed Ratio (OCR) values indicated poor performance of irrigation practices. From the analysis, it was found that the application of a fixed irrigation depth and fixed irrigation interval combinations of (25 mm—25 day), (20 mm—20 day), or (20 mm—25 day) are recommended for chat in the study area. Optimal irrigation schedules were decided on the basis of combination of irrigation interval and depth that results in low loss of irrigation water with reasonable yield reduction. Thus, determination of appropriate water management strategy can ensure proper utilization of the available water resources and improve the water application efficiency of the small-scale irrigation practices around Lake Alemaya, Ethiopia.     

Satellite Remote Sensing for Estimating Productivities of Land and Water

Satellite remote sensing offers the capability of objectively measuring spatiotemporalland surface parametersthat can provide information critical to irrigation performance studies. This study demonstrates the use of satellite remote sensing to identify the spatially distributed patterns of wheat yield and crop evapotranspirationfor the Bhakra command area (1.2 million ha), in the Haryana State of north-west India. For the first time, satellite remote sensing has been used to obtain estimates of productivity per unit of water consumed by crop evapotranspiration,a key indicator of the performance of irrigated agriculture. It is shown that areas with the highest grain yield correspond to the areas having the highest evapotranspiration.Consequently, the spatial variations in crop production per unit evapotranspiration are less (cv = 0.10) than spatial variations in productivity of land (cv = 0.17). Whereas head- and tail-end differences in three major branch canals were found for productivity of land, this trend was not detected for the productivity of water consumed. Causal factors for the spatial patterns of productivity need to be more thoroughly investigated. While calculation approaches are suggested to estimate productivity of land and water using satellite remote sensing, further research is required to refine these techniques. Better estimations of the productivity of land and water will allow for more detailed and objective performance studies at a range of scales from individual farm fields to entire irrigation schemes. It will help scientists understand productivity issues better, and enable water managers and policy makers to support improvements in the utilization of land and water resources.     

Effect of Subsurface Drip Irrigation on Cotton Plantations

During the cultivation periods of 2001 (a dry year) and 2002 (a wet one), an experimental cotton field was irrigated using a subsurface and a surface drip system. Both systems included drip-lines 17-mm in diameter, with emitters discharging 3.8 l/h and spacing 1 m. The treatments included four irrigation levels. These were equal to 120%, 100%, 80% and 60% of the net crop water requirements during each irrigation interval. For their calculation the FAO56–Penman–Monteith methodology that estimates crop evapotranspiration was utilised. From the statistical analysis of the harvested cotton plantations it has been found that during the dry year (2001) the seed cotton yields were significantly higher where the subsurface irrigation system was used and the irrigation applications met the 80% and 60% of the crop water needs. During the two experimental years the higher irrigation applications, 120% and 100% of the crop water needs, gave seed cotton yields that did not differ significantly for both systems (subsurface and surface).     

Estimation of Crop Coefficient and Evapotranspiration of Wheat (Triticum aestivum) in an Irrigation Command Using Remote Sensing and GIS

Remote sensing and Geographical Information System (GIS) techniques were used to estimate actual crop evapotranspiration of wheat crop grown in Tarafeni South Main Canal (TSMC) irrigation command of West Bengal State in India. The area under wheat crop was clipped from landuse/land cover map generated from Indian Remote Sensing Satellite P6 (IRS P6) image of January, 2004 for winter season 2003–04. The IRS P6 image and four wide field sensor (WiFS) images for different months of winter season were used to determine the Normalized Difference Vegetation Index (NDVI) and Soil Adjusted Vegetation Index (SAVI) for area under wheat crop. The relationship between vegetation indices and crop coefficients (K_c) of wheat for corresponding months were developed. Based on these developed regression equations crop coefficient maps were generated for each month of wheat crop season. Monthly reference crop evapotranspiration (ETo) was estimated based on FAO-56, Penman–Monteith method. ETo was combined with spatially distributed K_c maps of different months of wheat crop season to generate crop evapotranspiration (ET_c) maps of each month. The crop water demand of wheat estimated using spatially distributed ET_c maps for months of December 2003, January 2004, February 2004, March 2004 (1st Fortnight) and March 2004 (2nd Fortnight) were found to be 3.98, 8.14, 4.66, 2.49, and 1.21 million cubic meter (MCM) respectively. Based on crop evapotranspiration the total crop water demand of wheat crop in irrigation command of TSMC was estimated as 20.48 MCM.     

基于作物冠气温差的精量灌溉决策研究及其田间验证

根据相关研究结论和田间试验结果,构建了精量灌溉中基于作物冠层红外温度和土壤水分等模糊决策模型,并进行了冬小麦田间试验的实际运行和结果考核.结果表明,冠层红外温度是一个较好的反映作物水分状况的灌溉决策指标;冬小麦日内冠气温差的变化规律是在10点和14点出现双峰现象,最佳灌溉决策时机应该考虑到这两点的观测数据.充分考虑作物的水分信息状况和土壤水分情况(田持的60%时),将可以使作物的灌溉决策和管理达到“适时“和“适量“.所开发的基于作物红外冠层温度的精量灌溉决策模型,可以在进一步的试验观测基础上进行改进和完善,有较强的通用性和实用性.     

水塘系统对农业流域水资源调控的定量化研究

本文以一个典型农业小流域为对象，定量化研究水塘系统对流域因作物需水引起的水资源短缺的调控功能。结果表明，六岔河流域的水塘系统蓄水容量6.72万m3，在不同水文年均能有效地调控流域水资源的时空分布，满足作物生长需求。六岔河流域的多数降雨径流被水塘系统截留，减少流域径流输出；在连续流过程中，流域径流峰值急剧降低。水塘系统能够截留日降雨强度为144mm降雨产生径流的90%，径流峰值大大降低。由此说明水塘系统是雨水资源可持续利用的一种有效方法。     

Risk Assessment of Agricultural Water Conveyance and Delivery Systems by Fuzzy Fault Tree Analysis Method

Improving the efficiency of main Agricultural Water Conveyance and Delivery Systems (AWCDS) has a significant impact on improving water productivity in agriculture. Therefore, risk assessment of mentioned systems is necessary to increase reliability of operational performance. Accordingly, this study for the first time presents a unique framework to assess the adequacy, equity, and efficiency of agricultural water distribution and delivery risk assessment within AWCDS. In this way, the Fault Tree Analysis (FTA) technique is employed for risk assessment of “undesirability of supply and delivery”. The west Dez main irrigation canal in Khuzestan province of Iran was determined as the case study of the research. A set of questionnaires filled up by managers and experts of this irrigation district, the failure probabilities of the basic events are gathered in the form of linguistic terms. Due to the uncertainty in these terms, the system’s risk assessment to determine the failure probability of the top event was performed based on Fuzzy Fault Tree Analysis method (FFTA). The results of the study showed that the failure probability in the fuzzy approach is 0.55 which is roughly 0.15 more than crisp approach. Also, the rating of the basic events based on their contribution to the occurrence of the top event was carried out using importance measures. Five major events were identified with an emphasis on operational and socio-economic issues related to distribution and delivery of water. Comparing the results of risk assessment with the mathematical model reveals that the latter’s failure probability will be less than the system’s FTA due to non-consideration of some important factors.     

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。     

A multiobjective fuzzy linear programming model for sustainable integrated operation of a multireservoir system

Irrigated agriculture is the largest consumer of water, with high significance in India as the majority of its people depend on it. Rainfall uncertainties, and uneven distribution of utilizable water over space and time, have presented a serious challenge to irrigation water management and crop production. Surface water reservoirs play a major role in supplying irrigation water and also addressing uneven water distribution to some degree. Varying water requirements for different crops under multiple canals, however, requires that planners develop an optimal crop planning for the efficient operation of a multireservoir irrigation system. The spatial and temporal water transfer within a multireservoir irrigation system necessitates integrated operation of all the involved reservoirs. Thus, integrated operation of a multireservoir system is a fundamental requirement for efficient irrigation water management, and also become a key issue for sustainable agricultural development. This study derived an optimal crop plan for the integrated operation of a complex multireservoir system with intrabasin water transfer, using a multiobjective fuzzy linear programming (MOFLP) approach. The MOFLP model resulted in a level of satisfaction of 0.46, with an irrigation intensity of 102.18%, and a total crop area of 149 232.10 ha. The optimal policies were furthermore assessed with various statistical indicators with a simulation model, indicating they are performing well, with high reliability and resilience for longer periods.