Hydrological modelling of a small watershed using MIKE SHE for irrigation planning

The physically based distributed modelling system, MIKE SHE, is used to simulate the hydrological water balance of a small watershed with the objective of developing the irrigation plan. Simulation is first conducted over 109 days, concentrating the attention on the main cropping season, i.e., kharif (Jul–Oct), and the average water balance is calculated. It is observed that in spite of the frequent rainfall in the season, there are phases when the water content in the root zone goes below the allowable deficit. In case irrigation is not supplied during these periods, the yield of the paddy will only be about 70% of the potential yield. To attain the potential yield, the irrigation requirement is calculated as 490 and 340 mm for the upstream and downstream ends of the watershed respectively. Irrigation schedule for the purpose is suggested. Hydrological water balance simulation is further extended to the second cropping season, i.e., rabi (Nov–Feb), over 100-day period. Here, the water stored in the existing tank at the outlet is used for the supplemental irrigation in the season. It is seen that the actual yields obtained are very close to the potential yields of the selected crops. The results overall illustrate the applicability of a comprehensive hydrological modelling system for the management of water resources for agricultural purposes in a watershed.     

Towards Improved Performance of Irrigation Tanks in Semi-Arid Regions of India: Modernization Opportunities and Challenges

In the semi-arid regions of India there are around 120,000small-scale tanks, irrigating about 4.12 million ha. In manyareas, the tank storage structure is the only water source tostore rainwater and help farmers through crop growing periodand provide stability to agricultural production. Theunderdevelopment, stagnation and even decline of paddyagriculture during recent years in this region are usuallyattributed to the constraints in tank water supply. Whateverthe shortcoming at their creation, existing irrigation tanksremain an asset to the sustainability of irrigatedagriculture. The objective of this paper is to bring out thechallenges and opportunities towards improved performance ofirrigation tanks in semi-arid regions of India throughintegrated modernization. The performance of various types ofsmall scale irrigation tanks are evaluated for their role incrop production development strategies. The short-termstrategies include on farm development works throughmodernization of existing irrigation facilities/structures andconjunctive use of surface and groundwater resources. Thelong term challenges consist of establishing water gridsconnecting these modernized tanks in a chain to mitigatedrought and flood at local level as well as encouraging thefarmer's participation in planning and management of theseirrigation facilities for sustaining agriculture. It was foundthat evolving comprehensive but integrated modernizationstrategies for the tanks is a complex task, due to the dynamicinteractions of water.     

Tank Performance and Multiple Uses in Tamil Nadu, South India

Irrigation tanks in India are common property resources. Theland and water resources of tanks provide not only forirrigation, but also trees, fishing, domestic water supply,livestock, and a number of minor uses. Using empirical resultsfrom a study of tank performance from 80 tanks in Tamil Nadu,South India, this paper evaluates tank irrigation systemperformance both in terms of irrigation as well as irrigationand other multiple benefits. Ranking of tanks' performancechanges substantially, depending on which measure is used. Theresults indicate that taking other productive uses (excludingdomestic and livestock) into account, raises the total valueof output by approximately 13%, and increases the totalrevenue mobilized from tanks by 213%. Taking all revenue intoaccount tanks are not subsidized by the government, butcurrently fees are not channeled back to support tankoperations and maintenance.     

基于DEM模型的流域参数识别方法研究

探讨了利用数学高程模型识别流域分水线、确定坡面水流方向以及计算流域参数的方法。通过实验流域的数据验证 ,表明该法能正确计算流域的有关参数 ,自动勾绘流域分水线 ,确定坡面水流方向。从而为分布式水文物理模型的研制提供坚实的基础     

考虑水头损失的管道灌溉分水口轮灌分组优化模型

[目的]优化灌溉系统中分水口轮灌分组的灌溉制度,在满足流量要求的条件下节约电能.[方法]提出了在考虑水头损失时不同分水口状态与管道进口压力的关系模型,该模型利用分水口开关0,1状态作为自变量,从管道末端起利用推导的递推公式求出管道进水口的等效水头损失系数.依据该模型,在定流量分组轮灌优化中得到为使分组轮灌功率最小的目标...     

水资源开发利用总量控制的理论、模式与路径探索

"为什么要控制、控制什么、怎样控制"是实行水资源开发利用需要解决的重要科学问题,这些问题的回答对于我国推进和落实最严格水资源管理战略具有重要的价值。本研究首先揭示了水资源开发利用总量控制的基本概念;其次,提出了水资源开发利用总量控制的三大基础理论,即流域"自然-社会"二元水循环理论、分行业耗用水原理以及适应性管理理论,分别为水资源开发利用总量控制提供宏观边界条件、核心驱动力和动态实施依据;再次,提出了区域水资源开发利用总量控制"一核制约、双向协调、三层嵌套"的基本模式;最后,绘制了不同来水频率条件下区域水资源开发利用总量控制曲线,识别了缺水期和丰水期区域水资源开发利用总量控制的起点和路径。     

农田排水对塔里木河水质盐化的影响研究

在塔里木河流域农田排水的发展可以划分为三个阶段,即“旱排水”、排水渠建立和逐步完善阶段。农田排水虽对灌区内部的盐渍化治理起到了很大的作用,但排水进入河流对河水的水质盐化影响很大。所以应寻找新的排水出路,多途径排水。同时发展节水灌溉,改变传统的排水洗盐方式,才是干旱区农业发展的方向。     

Development of DRAIN-WARMF model to simulate flow and nitrogen transport in a tile-drained agricultural watershed in Eastern Canada

A new watershed model, DRAIN-WARMF, was developed to simulate the hydrologic processes and the nitrogen fate and transport that occur in small, predominantly subsurface-drained, agricultural watersheds that experience periodic freezing and thawing conditions. In this modeling approach, surface flow is simulated using a watershed scale model, WARMF, and subsurface flow is estimated using a field-scale model for subsurface-drained shallow water table fields, DRAINMOD 5.1. For subsurface flow calculations, the watershed is subdivided into uniform cells, and DRAINMOD is run on each cell with inputs based on the individual hydrologic characteristics of the cell. The coupling results in a distributed parameter model that calculates the total flow at the outlet of a watershed as well as the nitrogen losses. The model was evaluated for the St. Esprit watershed, located approximately 50 km northeast of Montreal. Simulations were carried out from 1994 to 1996; data from 1994 and 1995 was used for model calibration and data from 1996 was used for model validation. The new model was able to adequately simulate the hydrologic response and nitrate losses at the outlet of the watershed. Comparing the observed daily flow/monthly nitrogen with the model's outputs over the validation period returned an R² value of 0.74/0.86 and modeling efficiency of 0.72/0.83. This clearly demonstrates the model's ability to simulate hydrology and nitrogen losses occurring in small agricultural watersheds in cold climates.     

Tank performance and multiple uses in Tamil Nadu,South India–comparison of 2 time periods (1996–97 and 2009–10)

Irrigation tanks in India are common property resources. Tanks provide not only for irrigation, but also forestry, fishing, domestic water supply, livestock, and other uses. Using empirical results from a study of tank performance from 80 tanks in Tamil Nadu, South India in two time period: 1996-97 and 2009-10, this paper evaluates tank irrigation system performance in terms of economic output and revenue generation forirrigation and other uses. The results indicate that irrigation and other productive uses put together raised the total value of output at tank level by 12 % in 1996-97 and just 6 % in 2009-10. This may suggest that tank multiple use values are small and getting smaller, and therefore not worth consideration. However, it was also found that, while declining in absolute terms, non-irrigation uses provided the majority of tax revenues and still more than cover government's operation and maintenance expenditure (O&M) budget. This finding provides another reason to consider multiple use values and their linkage with overall system viability.     

A tool for community-based assessment of the implications of development on water security in hillside watersheds

Development and population growth in Latin American countries with steep slope farming are likely to further increase pressures on water and land resources. A methodology was developed for assessing water availability and use under different development pathways at a watershed scale to determine whether water security is a potential problem, and if so, under what conditions it is likely to occur. This methodology makes use of a GIS-based spatial water budget model for simulating stream water availability, water use and stream flow control on a daily basis at a watershed scale. Here, we analysed water availability under three plausible development scenarios for the 3246 ha Cabuyal River watershed in southwest Colombia in the year 2025: Corporate Farming (CF), Ecological Watershed (EW), and Business as Usual (BU). Simulated average river flows at the watershed outlet were, respectively, 874, 796 and 925 l s⁻¹ for the CF, EW and BU scenarios. The contribution of base flow to river flow (base flow index) was on average, 80.8, 85.6 and 77.9%, respectively, for the three scenarios. The watershed had the potential to meet the anticipated increase in water use under each explorative scenario. However, dams were necessary to store irrigation water in the CF scenario, otherwise over 60% of the available water would have been used during the dry season. Such a high figure raises concerns about effects on aquatic and riparian ecology, concentrations of potential contaminants, water reserves for especially low rainfall years, and the watershed resilience to meet temporarily higher water needs during the day. Analyses indicated that current water-use conflicts in the watershed can be resolved if irrigation water supply is separated from drinking water supply. This study helped reduce some of the complexity associated with the interdependencies between land and water resources, the impact of using them, and spatial linkages within the watershed. Results of this study can be used for teaching local stakeholders about basic landscape responses and helping multi-institutional alliances to become proactive and to guide development to the benefit of local communities.     

Salt movement,leaching efficiency,and leaching requirement

To study the salt movement in a soil profile, experiments were conducted on sandy loam and silty clay loam in tanks. The chloride concentration and electrical conductivity of the soil water were found from soil water samplers and salinity sensors. The standard deviation of the chloride concentration at each depth was small at the beginning of the percolation process when the soil was uniformly non-saline or highly saline; it increased strongly during the process and returned to its original value at the end. This points to a very heterogeneous water and salt movement through the soil profile. The chloride concentration, when increasing or decreasing rapidly, shows a large scattering. The effective mixing length in the tank experiments appears to be much greater than in laboratory soil columns. It varies between 10 and 15 cm in sandy loam and between 15 and 30 cm in silty clay loam. Irrigation water and soil moisture do not mix completely. An increasing part of the irrigation water moves through the soil without contributing to the leaching process. The results of the tank experiments agree with those of field experiments on similar soils. The consequences for the calculation of the leaching requirement in practice are discussed.     

Adjusted friction correction factors for center-pivots with an end-gun

A new method for calculating total friction head loss in center-pivots with an operational end-gun was developed. The proposed methodology is based on adjusting the previous friction correction factors for center-pivots with end-guns in order to correct their paradoxes and shortcomings. Equations presented in the current work are developed for center-pivots with a finite number of outlets along the lateral and constant outlet spacing and discharge as well as constant discharge and variable spacing. The proposed formulas depend on the number of outlets along the supply pipeline, the exponent of velocity term in the friction formula used and the distance that water is jetted by the end-gun. All equations reduce to the well-established equations for the friction correction factor when the end-gun is turned off. The equations presented here compare well to the stepwise friction calculation method, yet correct slight errors in the way that these friction correction factors were calculated in the past.     

Evaluating irrigation applied and nitrogen leached using different smart irrigation technologies on bahiagrass (Paspalum notatum)

Irrigation technologies [i.e., automatic timer, automatic timer with rain sensor, automatic timer with soil water sensor (SWS), and evapotranspiration (ET) controller] were compared in a bahiagrass plot study by measuring irrigation applied, water volumes drained, and NO₃–N and NH₄–N leached. All irrigation technologies were scheduled to irrigate on Sunday and Thursday. Three different irrigation depths were evaluated with the automatic timer: 15, 19, and 32 mm. SWS treatment allowed scheduled irrigation if soil water content was estimated to be below 70 % of water holding capacity, while the ET treatment allowed scheduled irrigation if soil water content was estimated to be below 50 % of plant available water. The rain sensor, SWS, and ET controller treatments applied significantly less water (p < 0.05) than the automatic timer treatment (which irrigates on specific days and times without regard to system conditions), reducing water by 17–49, 64–75, and 66–70 %, respectively. NO₃–N and NH₄–N were only significantly different after the second fertilizer application, which coincided with the 32 mm per event irrigation rate for the automatic timer treatment. Under these conditions, the automatic timer treatment had significantly greater NO₃–N and NH₄–N leachate than other treatments due to greater occurrence of soil water content exceeding water holding capacity, which resulted in drainage. Findings suggest that water can be saved using rain sensors, SWSs, or ET controllers and that leachate NO₃–N and NH₄–N can be reduced using rain sensors, SWSs, or ET controllers.     

景电一期灌区沟道退水滞后性

为揭示干旱区引黄灌区沟道退水滞后性规律,根据景电灌区沟道退水监测资料,采用交叉相关系数法和数据平移法确定灌区退水滞后时间,分析退水时空变化规律及其影响因素.研究表明,各退水口的年退水量差异不大,多年平均退水量约为4 622.3万m³,占灌溉引水量的31%.不同退水口之间的退水量差异较大,其中响水村占总退水的67%,五佛乡占总退水的30.6%,二期总一泵占总退水的2%.景电灌区不同退水口月退水量的主要影响因素为退水口控制面积和退水滞后时间,影响退水滞后时间的因素包括引水、降水、退水路径长度和人工开挖排水渠等.不同退水口的退水滞后时间在1~5个月之间,响水村退水滞后性较五佛乡和二期总一泵强,由灌溉和引水引起的退水滞后性有所差异.本研究所揭示的景电灌区退水滞后效应及其影响因素,可为灌区水资源合理配置与精准调控提供理论支撑.     

不确定性参数对水体纳污能力的影响分析

水体的水文条件、污染物降解系数、水质浓度、排污口概化方式等是影响纳污能力的参数。论文分析了各参数的不确定性特征,从理论上阐述了它们的影响机理,并通过实例定量分析了排污口概化方式、水文条件、降解系数、水质浓度等对纳污能力的影响。结果表明,在设计流量一定的情况下：采用均匀概化和中断面集中概化两种方式计算的纳污能力较为接近;采用集中概化方式进行计算时,纳污能力随概化点源到末断面距离的增加呈指数增长。目标水质浓度、初始水质浓度、降解系数和设计流速对纳污能力影响程度依次减弱。     

Estimating variable acreage of cultivated paddy fields from preceding precipitation in a tropical watershed utilizing Landsat TM/ETM

Given a suitable high and constant temperature regime, rice can be cultivated year-round in the tropics as long as water is available. Accordingly, multiple cropping is possible in such regions. The number of croppings per year varies depending on water availability and thus annual gross cultivated acreages are subject to fluctuation. The predominant causes of this fluctuation are related to seasonal and inter-annual variability in the volume of precipitation along with the hydrological characteristics of the watershed. We analyzed the effect of preceding precipitation on cultivated paddy field acreage in the Cidanau watershed, West Java, Indonesia. The analyses had two steps; first, the manipulation of eight Landsat images of different years to identify paddy fields cultivated in the entire paddy field area. There was difficulty in identifying cultivated paddy fields because of the coexistence of various growth stages of rice; however, early growth stage paddy fields were successfully distinguished from uncultivated fields using middle infrared band values due to surface reflectance of flooded water, while more advanced growth stage fields were identified with Normalized Difference Vegetation Index values. The second step was implementation of a linear regression model to the cultivated paddy field ratio with the cumulative volume of preceding rainfall as a single independent variable. The result confirmed that there was a strong correlation between 90-day cumulative rainfall and cultivated paddy field acreage as identified by satellite images, where “90-days” implies the lifespan of paddy rice after transplantation. However, the sensitivity of cultivated paddy fields to the preceding rainfall ratio varied among sub-watersheds due to variations of hydrological characteristics and the storage capacity of the particular water source.     

基于单片机的沼气发酵装置增温控制系统设计

设计单片机控制系统提高沼气池的温度,使产气量增加。本文以单片机AT89C51为核心,配以检测电路、温控电路、报警电路、显示电路组成温度控制系统。通过对加热装置的控制实现对贮水箱的加热,通过水泵把贮水箱中的水循环起来,使贮水箱中的水通过热置换器,把热能传递给沼气池,使沼气池温度升高,达到产生沼气的温度,使沼气池能连续产生沼气。结果表明若检测温度小于键盘设定温度,单片机控制可控硅使贮水箱温度升高,通过水泵把贮水箱中的水循环起来,使沼气池温度升高。若环境温度高时,贮水箱中的水可作为日常用水使用,加大了储水量。在实际应用过程中,该系统确实能实现沼气池的增温,确保了产生沼气的连续性,提高产气率。     

基于MIKE21模型的长江中环排污口水质影响分析

入河排污口设置论证工作对于预防流域水污染、保护长江水生态环境有重要意义。入河污染物的排放影响分析是排污口设置论证的重要工作之一。采用MIKE-21模型,建立了荆州中环污水处理厂排污口所在长江河段二维水动力学和水质扩散模型,模拟污水中COD、BOD5、氨氮等主要污染物在长江河段中的迁移和扩散情况,分析污水排放对长江水质的影响范围和影响程度。结果表明:MIKE-21模型对入河污染物的扩散过程模拟精度较高,模拟成果合理,基本反映了排污口污水排放对所在江段的水质影响情况,可作为排污口设置论证的参考依据。     

Irrigation water management for crop diversification: Application of the WACCROD model

The actual water management practices, in terms of the volumes and intervals of delivery, are examined in a rice-based irrigation subsystem where crop diversification is practised. A simulation model (WACCROD) is used to generate the hypothetical water requirements of the changing crop mixture at quartenary and tertiary levels.Crops other than rice were planted in the dry season to reduce the need for water. Then, as the available water supplies diminished, the volume and timing of water deliveries changed based on the time, hydraulic location and relative importance of the crop.     

农田流域水文响应特征分析及模型考虑

农田流域由于下垫面性质的复杂和农业管理活动对水文循环的影响,表现出了与自然流域不同的水文特征。通过对农业水文、农田水利方面的相关研究进行总结,从农田流域典型下垫面和农业管理活动2个角度,分析农田与自然流域水文响应差异,提出建立基于农田水文系统特征的分布式流域水文模型的若干考虑。