Flexibility analysis of irrigation outlet structures using simulation of irrigation canal hydrodynamic model

The Upper Swat Canal (USC) System became operational in 1917–1918 in North West Frontier Province (NWFP) of Pakistan. The rehabilitation and modernization of the USC was undertaken with a view to overcoming the shortage of water supplies for irrigation. The water allowance was enhanced from 0.39 to 0.77 Ls⁻¹ ha⁻¹ in the study area. Recently, the operation and management of a secondary canal or ‘distributary’ was transferred to the Farmers Organization (FO). This distributary named ‘Chowki’ offtakes from the Maira Branch of the USC. The cultivable command area (CCA) of this distributary is 4,306 ha and it serves 1,485 beneficiaries. A management committee on Chowki Distributary was formed in 2003. This distributary consists of one main and two minor channels having twenty-eight direct outlets. The Simulation of Irrigation Canal (SIC) hydrodynamic model was used to evaluate the flexibility of Chowki Distributary. The model was calibrated at 100, 80 and 70% of the design discharge (Q _d) and it was validated at 90, 85 and 60% of the design discharge. The observed and simulated water levels were in close agreement with each other for the calibration and validation periods. The statistical analysis and paired t-test indicate that the model results are not statistically different from the measured values at 1% significance level. The simulated results of the SIC model were applied to studying flexibility of the outlet structures along the Chowki Distributary. The flexibility analysis demonstrates that poor performance is inbuilt into the system due to inadequate control over the accuracy of the crest setting during the construction of the outlets.     

美国德克萨斯州高地平原区地下水灌溉管理方法研究

德克萨斯州高地平原区是美国灌溉和旱地作物的生产基地,其灌溉水源主要来源于奥加拉拉(Ogallala)地下水含水层。然而,自从1950年灌溉农业发展以来,由于对奥加拉拉含水层地下水的过度开采,使得区域地下水位严重下降,有些地区地下水位下降超过50 m。为了保护地下水资源和实现地下水可持续利用,2000年以来美国德克萨斯州高平原地区在节水压采方面开展了一系列工作,取得了较好的成效。采取的主要措施包括:用德克萨斯州高地平原蒸腾蒸发网络(The Texas High Plains Evapotranspiration Network, TXHPET)进行灌溉及地下水管理,改变作物品种,改进灌溉技术,改变种植结构,保护性耕作方法,加强降雨管理,将小部分灌溉农田转为旱作农田等。该区域1958年的灌溉面积为183万hm~2,1974年灌溉面积达到峰值,为242万hm~2;1989年灌溉面积降为159万hm~2,由于喷灌技术的推广应用,2000年灌溉面积恢复到187万hm~2。1958年大多数灌区为地面灌溉,仅有11%的灌溉面积为喷灌。1974年之后,灌溉总面积在减少,主要灌溉方式转为喷灌,中心支轴式喷灌面积稳步增长。自1989年之后,喷灌在该区域快速发展,2000年喷灌面积已占该区域灌溉面积的72%。早期的喷灌系统在较高压力下运行,自20世纪80年代,低压喷灌系统已全面使用。我国华北地区长期超量开采地下水与美国德克萨斯州高原区地下水超采情况及问题相似。兹系统介绍了美国德克萨斯州高地平原区在地下水超采情况下采取的综合措施拟为我国地下水超采地区的地下水管理工作提供技术与经验参考。     

Temporal and spatial dimension of dissolved oxygen saturation with fluidic oscillator and Mazzei air injector in soil-less irrigation systems

The wider scale use of aerated water for irrigation has been limited by dis-uniformity of aeration in the field, limited longevity of oxygen in irrigation water and lack of knowledge of what oxygen concentration brings optimal growth. Two options are presented for increasing dissolved oxygen (DO) in irrigation water: Venturi (VT) and fluidic oscillator (FO) aeration systems. Sweet corn was grown in pots to evaluate the effect of aerated water. Compared to the control treatment (CK), VT and FO showed an increase in irrigated water DO in the irrigation tank and feeding pots after aeration. Incorporation of surfactant in the irrigation water significantly improved DO level for the VT and FO treatment. Typically the DO levels reached a peak when the pump is turned off and then decline to a minimum after 24 h. The VT and FO systems had a higher magnitude and duration of the DO level in the water in all treatments compared to the CK system. The FO aeration maintained the longest duration of elevated DO in the water by a factor of two compared to the VT aeration. Compared to the CK, the best result on longevity and DO concentration was achieved using 4 ppm of a non-ionic surfactant. The corn biomass was significantly greater for the VT compared to both the FO and CK treatments.     

Participatory water management at the main canal: A case from South Ferghana canal in Uzbekistan

After the independence of Central Asian countries, many international projects have been launched to promote water users’ inclusion into the water management at different levels. The aim of such projects is to achieve sustainable water management through inclusion of interests of different groups on day-to-day water management. Although IWRM in Central Asia has been already promoted for a decade, there are only a few examples of the implementation in real life situations.The Integrated Water Resources Management in Ferghana Valley (IWRM FV) is a pilot project on implementing integrated water resources management elements at the main canal levels and below. The experience gained from IWRM FV project and lessons learnt could be useful for the national and international organizations for their future work on IWRM implementation at the different regions of Central Asia.IWRM FV project has been active since 2001 in the Ferghana Valley, one of the largest irrigated areas of Central Asia. The project has promoted and implemented participatory irrigation management for three pilot canals. This paper presents the process of implementation and some preliminary outcomes of the IWRM VF project.     

Study of feasibility of night-closure of irrigation canals for water saving

The feasibility of closing distributary canals at night was investigated in a recently modernized surface irrigation system in Pakistan, the Upper Swat-Pehur High Level Canal system. Increased water supply, greater delivery capacity and the introduction of downstream control potentially allow more flexible service. In the command area of Maira branch of this system, farmers are anyway abandoning night-time irrigation, as they can meet their needs from improved supply during the day. They practice night irrigation only during the times of peak crop water demand. The rotational delivery system, known as warabandi in the sub-continent and Dauran in Arabian countries, has even broken down in the day in some parts of the command area. This is believed to be typical of systems with more than adequate water supply.A simulation study was undertaken using the CanalMan software developed by Biological & Irrigation Department, Utah State University, Utah Logan, USA. Primary data collected in one distributary canal and the two minors connected to it was utilized for simulations. The feasibility of night-time closure depends on the speed of filling and emptying the canal each day, and the time required to meet full irrigation demand during the day. The results show that where canal lengths are less than 5 km, in this system, there is good potential to make savings, which can be realized at system level through reduced demand on supplemental supplies from Tarbela Dam.     

Application of a hydraulic model for testing management decisions at distributary level

Summary This study was conducted on the Lagar Distributary of Gugera Branch of Lower Chenab Canal, Punjab, Pakistan. A computer model MISTRAL was adopted for evaluating management options. The study showed that the model can be used as a decision support tool for prioritizing management options. The model suggests that under current physical conditions of this distributary the combination of rotation between the distributaries and along the distributary canals can improve the equity of water discharge. For example, in case of Lagar Distributary the discharge of tail outlets can be increased threefold by introducing rotation between the tail of the distributary and an offtaking minor canal. A small decrease in the discharge of the minor would result from adopting this option. A combination of rotations between this and neighboring distributaries and along the Lagar itself can increase the discharge of tail outlets up to seven times. The results of the model indicate that operational changes can improve the discharge of tail outlets to some extent, but the improvement of physical conditions of the distributary is needed to achieve equity conditions, as specified in the design.     

Rising water table: A threat to sustainable agriculture in an irrigated semi-arid region of Haryana, India

The sustainability of the rice-wheat cropping system in an irrigated semi-arid area of Haryana State (India) is under threat due to the continuous rise in the poor quality groundwater table, which is caused by the geo-hydrological condition and poor irrigation water management. About 500,000 ha in the State are waterlogged and unproductive and the size of the waterlogged area is increasing. We analyse the hydrology and estimate seasonal net groundwater recharge in the study area. Rainfall is quite variable, particularly in the monsoon season, and the mean monthly reference evapotranspiration shows a high inter-annual variation, with values between 2.45 and 8.47 mm/day in December and May. Groundwater recharge analysis during the study period (1989-2008) reveals that percolation from irrigated fields is the main recharge component with 57% contribution to the total recharge. An annual groundwater table rise of 0.137 m has been estimated for the study area. As the water table has been rising continuously, suitable water management strategies such as increasing groundwater abstraction by installing more tubewells, using the groundwater conjunctively with good quality canal water, changes in cropping patterns, adoption of salt tolerant crops, changes in water-pricing policy, and matching water supply more closely with demand, are suggested to bring the water table down to a safe limit and to prevent further rising of the water table.     

Conjunctive use of canal and groundwater in Punjab,Pakistan: management and policy options

Data from 41 watercourses commands in Pakistan show that, as expected, farmers in head end reaches of canals receive more canal water than those in tail end reaches. Contrary to conventional wisdom, however, these head end farmers also use more groundwater than those at the tail end. Overall, groundwater plays a more important role in irrigation than surface water, ranging from 65% dependence on pumped water in head end areas to over 90% in tail end areas. This means that groundwater is no longer supplemental to canal water, but is an integral part of the irrigated agricultural environment. However, the cropping choices of farmers appear to reflect the amount of good quality canal water they receive: head end farmers are able to grow more high value basmati rice in the summer and more vegetables in the winter, leaving tail enders to rely on less valuable crops such as fodder and wheat.Tail end areas are not only deprived of their fair share of surface water: they have to pump proportionately more groundwater which shows decreasing quality towards the tail. Typically, head end areas have groundwater with EC values of less than 1.0 dS/m, rising to over 2.0 dS/m in tail end areas. When the quality of both surface and groundwater used by farmers is examined, only the top 40% of the distributary gets water of adequate quality, the next 40% get below average quality, while the tail 20% of farmers irrigate with water that is classified as saline.Because of higher dependence on more expensive groundwater tail enders use less water per unit area, thereby reducing the leaching requirement. The result is a clear increase in soil salinity from head to tail along distributary canals, and there is some evidence of land abandonment in tail end watercourses due to excess salinity.The implications of these results are far reaching. Government policy includes plans to divert significant quantities of fresh canal water to areas underlain by saline groundwater on the basis that farmers already have adapted to pumping fresh groundwater. The results reported suggest that if this policy were implemented, there is a risk that over-dependence on fresh groundwater could lead to an intensification of the rate of soil salinization and deterioration of quality in areas currently classified as fresh groundwater zones.At present, the location and utilization of privately owned shallow tubewells is not monitored, and thus it is not possible for government agencies to determine just how much water of different qualities is being used. Further, canal water deliveries, public deep well monitoring, watercourse monitoring programs, soil salinity measurements, and agricultural performance monitoring are all scattered among different agencies and organizations, making the task of effective conjunctive management of surface and groundwater even more difficult.Conventional wisdom: Groundwater in Pakistan ... where it exists within the canal system ... is used to supplement surface water supplies to meet peaks in demand. (WAPDA, 1990)     

Equity of water distribution along secondary canals in Punjab,Pakistan

Equity in the distribution of irrigation water has long been an operational objective for the management of the large canal systems in the north and west of the Indian subcontinent. How well that operational objective continues to be met is the central concern of the research reported in this paper. Detailed studies of canal operations were conducted on three distributaries in the Lower Chenab Canal system in Punjab Province, Pakistan. Mananwala and Lagar Distributaries off-take in the head reach of the Gugera Branch Canal and Pir Mahal Distributary is at the very tail of this Branch. Flow conditions for these distributaries and of selected outlets served by each were measured daily throughout 1988, and data were converted to discharges. These field observations show that discharge variation at the head of distributaries greatly exceeds the original design criteria. The data also indicate that two design assumptions for outlets are no longer valid: continuous full supply water level in the distributary and outlet modular flow conditions. Field measurements confirm that the distribution of surface water among the outlets of all three distributaries is substantially inequitable. Outlets in the channels' head reaches commonly draw 3 to 6 times greater share of total supplies than do tail outlets. Although all three selected distributaries are perennial canals, some outlets remained dry for up to 90% of the total operational days in a year. Finally, evaluation of field data also shows that better operational procedures at the distributary level can substantially improve water supply conditions in the tail reaches.     

Comparing water management in rice-wheat production systems in Haryana, India and Punjab, Pakistan

The intensive irrigated rice-wheat systems in the northwest Indo-Gangetic Plains of South Asia are built on a long tradition of canal irrigation and the more recent advent of tubewells. Findings from farm surveys are used to examine water management and water productivity in the rice-wheat belt of India's Haryana State and Pakistan's Punjab province. Attributes of the irrigation sources help explain the widespread interest in groundwater use and the relative demise of canal water use. In each area groundwater now is the main irrigation source, used either solely or in conjunction with surface water. The ownership of tubewells is near universal among the surveyed farms, whereas conjunctive water use is more widespread during the monsoon season, among better endowed farmers and in the Pakistan Punjab. In Pakistan Punjab farmers primarily rely on diesel powered tubewells whereas Haryana farmers mainly use relatively cheaper electric power. Water productivity indicators for rice are markedly lower than those for wheat—largely reflecting significantly higher water inputs in paddy cultivation—but also vary between the study areas and by the prevailing water use, reflecting the limited incentives for farmers to use water wisely. A combination of technological, land use and market based approaches is likely to be most effective in achieving sustainable water management in these intensive cereal systems.     

Modeling approach for the assessment of recharge contribution to groundwater from surface irrigation conveyance system

Rice–Wheat rotation system utilizes surface, ground and rain water resources conjunctively. Recent studies have shown increasing contribution of groundwater for crop irrigation. As the system utilizes water pumped from the underlying aquifer and partly seeps back, a cycle of recharge and discharge continues. Sustainability of groundwater system for the on-going drought in the country depends mainly on the recharge of the aquifer. The reported study was, therefore, carried out to measure and assess the recharge contribution of a distributary of canal in Punjab, Pakistan. Assessment of recharge through distributary was carried out using a groundwater flow “MODFLOW” model, which utilized the observed watertable, climatic, crop and soil for a period of about 1 year in addition to hydraulic conductivity, evapotranspiration and aquifer characteristics data. The requisite primary data for “MODFLOW” were collected from field and secondary data from public sector organizations dealing with water. Model calibration involved changing input parameters within reasonable limits until acceptable matches were obtained between the observed and simulated water levels for all observed hydrographs. The external inputs such as, recharge through irrigation, precipitation, stresses due to evaporation, lateral flow and stream were simulated to calculate the monthly water budget of aquifer. As concluded, recharge contribution was 16.5% of the inflow rate of the distributary. Using predicted results of the model a relationship between recharge (R) and discharge (Q) was also developed. Although, the presented results of recharge contribution were limited to one distributary of canal irrigation system, yet the developed methodology can be extended to the other canal systems of the Indus Basin.     

Yield measures of irrigation performance in Pakistan

Customary evaluations of irrigation performance based upon crop yield per unit area do not reflect an adequate assessment of performance in water scarce environments such as Pakistan. Yield per unit water is a complementary and sometimes more appropriate measure. This note illustrates the different evaluations based upon yields of irrigated wheat and rice in Pakistan.     

宁夏灌区续建配套与节水改造项目良田渠治理措施

宁夏引黄灌区历史悠久,是我国大型灌区之一。自实施宁夏引黄灌区续建配套与节水改造项目以来,灌区骨干工程安全状况有了较大改善,渠道综合调控能力不断增强,灌区节水意识进一步提高。良田渠灌域是青铜峡河西灌区的组成部分,通过渠道砌护及建筑物新建、维修等改造工程措施,提高灌溉水利用系数,减少引黄水量,完善渠道防洪体系,为渠道提供安全的行水条件。对灌区经济持续发展和工程效益的充分发挥起到推动作用,同时对改善渠道沿线生态环境和城市美化也具有积极意义。      

Implementing irrigation: Salt and nitrate exported from the Lerma basin (Spain)

The creation of a new irrigated area influences the pollutants exported from the zone and, consequently, the quality of receiving water bodies. The aim of this study was to analyze the masses of the main pollutants exported by an area before and during its gradual transformation into irrigated land. To this end, salinity balances were carried out and the nitrate exported from the Lerma basin (752 ha, Spain) was quantified during 2004–2008. The agroenvironmental impact was evaluated through the use of pollution indices. The results revealed that the transformation of the area into irrigated land decreased salinity and increased nitrate concentration in drainage. The increase in the volume of drainage increased the masses of salt and nitrate exported, which in turn increased pollution indices during the transition. However, these indices were still lower than those quantified in other irrigated lands and therefore can still be considered to be of low contamination level. This study demonstrates the important environmental influence of introducing irrigation to an area, as pollution levels change and become mainly dependent on the management of irrigation and nitrogenous fertilization. For this reason, it is highly desirable to promote the optimization of agricultural management in a way that minimizes its impact.     

Soil–water and solute movement under precision irrigation: knowledge gaps for managing sustainable root zones

Precision irrigation involves the accurate and precise application of water to meet the specific requirements of individual plants or management units and minimize adverse environmental impact. Under precision irrigation applications, water and associated solute movement will vary spatially within the root zone and excess water application will not necessarily result in deep drainage and leaching of salt below the root zone. This paper estimates that 10% of the irrigated land area (producing as much as 40% of the total annual revenue from irrigated land) could be adversely affected by root zone salinity resulting from the adoption of precision irrigation within Australia. The cost of increases in root zone salinisation due to inappropriate irrigation management in the Murray and Murrumbidgee irrigation areas was estimated at AUD 245 million (in 2000/01) or 13.5% of the revenue from these cropping systems. A review of soil–water and solute movement under precision irrigation systems highlights the gaps in current knowledge including the mismatch between the data required by complex, process-based soil–water or solute simulation models and the data that is easily available from soil survey and routine soil analyses. Other major knowledge gaps identified include: (a) effect of root distribution, surface evaporation and plant transpiration on soil wetted patterns, (b) accuracy and adequacy of using simple mean values of root zone soil salinity levels to estimate the effect of salt on the plant, (c) fate of solutes during a single irrigation and during multiple irrigation cycles, and (d) effect of soil heterogeneity on the distribution of water and solutes in relation to placement of water. Opportunities for research investment are identified across a broad range of areas including: (a) requirements for soil characterisation, (b) irrigation management effects, (c) agronomic responses to variable water and salt distributions in the root zone, (d) potential to scale or evaluate impacts at various scales, (e) requirements for simplified soil–water and solute modelling tools, and (f) the need to build skills and capacity in soil–water and solute modelling.     

Effect of long-term un-treated domestic wastewater re-use on soil quality, wheat grain and straw yields and attributes of fodder quality

In 2006 a comprehensive sampling program was undertaken in two pre-selected peri-urban villages in Faisalabad, Pakistan to evaluate the soil and agronomic impacts of long-term (25–30 years) untreated wastewater re-use on wheat grain and straw yields and attributes of wheat straw fodder quality. Soil SAR, ESP, RSC and ECe were 63%, 37%, 31%, and 50% higher under wastewater (WW) as compared with canal water (CW) irrigated plots. Further, 2.7 and 6.65 fold increases in soil NO ₃ ^? + NO ₂ ^? - N and Olsen-P were observed in WW as compared with CW irrigated plots. However, no significant differences in grain yield, wheat straw biomass, or fodder quality attributes were observed between WW and CW irrigated plots. In addition, for both CW and WW irrigated plots wheat straw, Cd and Pb concentrations were orders of magnitude below the EC Maximum permissible levels for Pb and Cd in feed materials and thus pose no threat to the fodder-livestock food chain. Further, elevated soil N associated with WW irrigated plots has a significant (p?<?0.01) positive influence on fodder quality by increasing the N content. Factorial ANOVA with covariance indicates that effective management of the elevated soil ECe in WW irrigated plots would increase grain yield and wheat straw biomass by 853 kg ha^?1 (19.5%) and 819 kg ha^?1 (18.6%) respectively as compared with CW irrigated plots. In Faisalabad, if managed appropriately to address emerging salinity issues the contribution of wastewater irrigation to the achievement of MDGs 1 and 7 could be significant if adverse impacts remain as marginal as found in this study.     

Limits to agricultural growth in the Sistan Closed Inland Delta,Iran

The Sistan Delta in Iran is located at the end of a closed basin with nearly 100% of the supply coming from Afghanistan. This supply is supporting irrigated agriculture in the area and is the source for the lake system around the delta. These Hamoun lakes are ecological very valuable wetlands; a number of them are registered as Ramsar sites. The Iranian government tries to improve the living conditions of the people in the area, among others by providing infrastructure for irrigated agriculture. Further development of the irrigated area will mean less water for the Hamouns with resulting lower average water coverage of the lakes. This will not only endanger the ecosystem that the Hamouns support but also the livelihoods of the people that depend on the goods and services that the lakes provide. This paper describes a study that has been carried out to support decision making on potential development schemes in the delta. The non-availability of data from Afghanistan requires the development of various tools and the use of remote sensing techniques to enable to make estimates for the river flow that Iran can expect from Afghanistan. An IWRM approach has been used for the balancing of interests involved. Some preliminary conclusions are described.     

A study of water distribution from a branch to distributary canals: A case study of Gugera Branch,Punjab, Pakistan

This study was conducted on Gugera Branch of Lower Chenab Canal, Punjab, Pakistan. Sample distributaries off taking from Gugera Branch were selected for the study. The existing conditions of water distribution among the distributaries were studied. Field data were collected during the whole of 1988. Field observations suggested that the variability at the head of distributaries is much greater than the variability in the Gugera Branch under existing operational practices. The distribution of water among the distributaries is rarely in accordance with design criteria. Some channels get priority over other channels. The annual closure period varied from 17 to 41 days for different channels. The discharge at the head of distributaries remained lower than the standard operational range for 69 to 183 days in a year. The data suggested that a regulating gate at the head of the distributary can reduce discharge variation up to 2.4 times compared with a Karrees System (wooden stop logs used for water regulation). The data indicated that the adjustments in the head gate of a distributary on daily basis can substantially improve discharge conditions at the head of distributary. Rotational schedules are not being followed as per design and need to be improved. Most of the existing head discharge relationships of discharge measuring structures are not reliable. A frequent calibration of these structures is recommended.     

基于GIS的灌区计量与水管理系统研究

本文针对潇河灌区管理手段落后、水资源利用率低等制约灌区节水发展的瓶颈问题,从支持灌区科学用水管理的角度出发,运用先进的GIS平台,通过计算机网络传输,建立起潇河灌区计量与水管理系统.