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1.
《Agricultural Water Management》2004,69(1):43-67
A trial was conducted to examine the effects of retaining drain water with a weir on reducing acid flux from a drained coastal acid sulphate soil backswamp. Prior to weir construction, groundwater seepage to the ditch drain was the main hydrological pathway for acid flux. High hydraulic conductivity (>120 m per day) in the sulphuric horizons due to extensive macropores, combined with tidal modulation of drain water levels encouraged rapid seepage of acid groundwater. Most seepage occurred while the backswamp groundwater table was in a narrow elevation range, referred to as an ‘acid export window’. The acidity of drainage water was highly sensitive to the hydraulic gradient between the groundwater table and the adjacent drain water level. Acid flux rates from groundwater seepage were strongly positively correlated to effluent groundwater hydraulic gradients. The constructed weir was designed to reduce the magnitude of effluent groundwater gradients and retain shallow groundwater by maintaining high and stable drain water levels. This reduced groundwater seepage to the drain and increased the proportion of shallow groundwater lost from the system via evapotranspiration. The weir affected 60% of drainage network and observed and modelled data suggest acid flux from groundwater seepage was reduced by about 65–70%. Effluent groundwater gradients behind the weir were reduced by about 80%. The main effect of the weir was to reduce discharge volumes, although reductions in H+ and acidic metal cation concentrations were also observed. This study demonstrates that a weir can be an effective means of reducing acid flux in coastal acid sulphate soils where main hydrological pathway of acid export is groundwater seepage. However, this strategy may not prevent continued sulphide oxidation. Reduced acid export, but continued acid generation, combined with enhanced evaporative flux has the potential over the longer term to increase the net accumulation of acidic products in the backswamp soil and groundwater. Further monitoring is required to assess this possibility. 相似文献
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仇学明 《中国农村水利水电》1993,(3)
挖方或傍山衬砌的渠道,往往因地下水的挤压使渠底板开裂、鼓泡掉块、翻倒等。为保证渠道稳定,湖南省水科所研制出 ZM 系列渠道防渗减压阀.其基本构造为:在聚氯乙烯硬塑管模内,装入单向排水的逆止阀,管的两端用土工织物封盖。其性能良好,适用范围广,能有效地排除地下水压力对防渗层的破坏,而渠内过水时水流不外渗。 相似文献
4.
Recharge to the aquifer through seepage from irrigation canals is often quoted as one of the main causes for waterlogging
in Pakistan. In the design of drainage systems to control this waterlogging, rules-of-thumb are often used to quantify the
seepage from canals. This paper presents the option to use a groundwater model for a more detailed assessment. Groundwater
models may assist in evaluating the effect of recharge reducing measures such as interceptor drains along irrigation canals
and lining. These measures are commonly aimed at reducing the drainage requirement of adjacent agricultural lands.
In this paper an example is given of the application of a numerical groundwater model, aimed at assessing the effect of interceptor
drainage and canal lining in the Fordwah Eastern Sadiqia project, being a typical and well-monitored location in Pakistan.
The paper also presents references to other conditions. The model was used to obtain a better insight in the key hydraulic
parameters, such as the infiltration resistance of the bed and slopes of irrigation canals, the drain entry resistance of interceptor drains and the hydraulic conductivity of soil layers. The model was applied to assess the effectiveness and efficiency of interceptor drains under various conditions.
The results of the study show that the net percentage of intercepted seepage is too low to have a significant effect on the drainage requirement of the adjacent agricultural lands. Besides, the operation
of the system, with pumping required, is often an added headache for the institution responsible for operation of the system.
The marginal effect of interceptor drains and lining on the drainage requirement of adjacent agricultural land does not always
justify the large investments involved. It can be concluded that:
Relevant hydrological concepts and modelling parameters with respect to leakage from irrigation canals and interception by
interceptor drains are presented in a separate paper. 相似文献
| • | Use of rules-of-thumb to estimate components of the water balance of irrigation systems in designing drainage can be very misleading; |
| • | Interceptor drainage may cause induced seepage from irrigation canals, which is often an order of magnitude more than the net intercepted seepage; |
| • | Interceptor drains and canal lining do not significantly reduce the drainage requirements, or in other words, cannot prevent the need for the installation of a drainage system; |
| • | A numerical model can aid to evaluate proposed measures and strategies to alleviate water losses and drainage problems. |
5.
抽水蓄能电站建设中的尾水隧洞开挖可能引起的周围地下环境的变化,在水文地质条件和工程地质特征的分析的基础上,研究了文登抽水蓄能电站工程区地下水分布特征和平硐、尾水隧洞开挖引起的强排水特征,概化出工程区水文地质概念模型,建立了工程区地下水三维非稳定渗流模型。采用求解有自由面渗流场的改进的截止负压法、改进的排水子结构法、管道子结构法和预处理共轭梯度法等理论对文登抽水蓄能电站平洞开挖和尾水隧洞开挖（衬砌后）不同施工阶段的非稳定渗流场进行了数值模拟分析。研究了尾水隧洞开挖（不衬砌）后、尾水隧洞开挖衬砌后这两种方案下地下水渗流场动态变化过程及对周围地下水环境的影响。计算结果表明：①平硐和水道系统开挖对研究区地下水位下降有着直接的影响,且影响较大。②尾水隧洞衬砌300d后,地下水流场基本恢复至稳定状态。 相似文献
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为查明河南省新乡市浅层地下水的污染机理,通过现场调查并对地下水、地表水进行采样,测定其氢、氧稳定同位素及水化学成分,对水样的氢氧同位素和水化学组成的空间分布规律进行了分析。结果表明:降水是地下水的主要补给源。太行山区是剥蚀丘陵岗地地下水的主要补给区;中部冲洪积平原地下水受共产主义渠水的影响,二者同位素值较接近;受黄河灌溉回归水的影响,南部冲积平原地下水氢氧同位素值较接近黄河水,是大气降水和黄河水的混合水体。而研究区地下水污染除与地表污水侧渗、污染物通过包气带直接下渗有关,还与不合理开采地下水导致盐分和污染物的迁移有关。 相似文献
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Modelling the effect of canal bed elevation on seepage and water table rise in a sand box filled with loamy soil 总被引：2，自引：0，他引：2
The HYDRUS 2D finite difference two-dimensional water balance model was experimentally tested for transient and steady state
seepage flux, mound height, and piezometric water level from soil surface as a function of time and horizontal distance from
the centre of the canal (half width = 45 cm) under different canal bed elevations (20, 0, −40, −80 and −120 cm denoted as
experiments D1, D2, D3, D4 and D5, respectively) and constant water head of 5 cm in a sand box (200 cm × 170 cm × 150 cm)
filled with Hisar loam soil. Differences of means between measured and predicted values of infiltration flux, seepage flux
and mound height as tested by paired t test were not found significant (P = 0.05). Seepage flux and mound height increased with increasing canal bed elevation. Phreatic level depths were everywhere
much shallower than the piezometric water level depths in experiments D1, D2 and D3. However, in experiments D4 and D5 both
phreatic and piezometric levels were at similar depths. The seepage parameters and mound height increased, and water table
depth decreased, linearly with increasing canal bed elevation. Lowering the canal bed to 120 cm below the soil surface reduced
the seepage rate to that of lined canals. The projections in a large flow domain also revealed that lowering the canal to
−2 and −4 m below soil surface stabilized the water table at 2.5 and 4.5 m below soil surface, respectively. The practical
implications are that open drains should be used for irrigation in areas underlain with a brackish groundwater aquifer and
gravity canals may be allowed only where groundwater aquifer is of good quality and sub-surface water withdrawal is practiced
for irrigation. 相似文献
10.
Waterlogging and salinization are major impediment to the sustainability of irrigated lands and livelihoods of the farmers, especially the smallholders, in the affected areas of the Indus Basin. These problems are the result of a multitude of factors, including seepage from unlined earthen canals system, inadequate provision of surface and subsurface drainage, poor water management practices, insufficient water supplies and use of poor quality groundwater for irrigation. About 6.3 million ha are affected by different levels and types of salinity, out of which nearly half are under irrigated agriculture. Since the early 1960s, several efforts have been made to improve the management of salt-affected and waterlogged soils. These include lowering groundwater levels through deep tubewells, leaching of salts by excess irrigation, application of chemical amendments (e.g. gypsum, acids, organic matter), and the use of biological and physical methods. However, in spite of huge investments, the results have in general been disappointing and the problems of waterlogging and salinity persist.This paper reviews sources, causes and extent of salinity and waterlogging problems in the Indus Basin. Measures taken to overcome these problems over the last four decades are also discussed. The results reveal that the installed drainage systems were initially successful in lowering groundwater table and reducing salinity in affected areas. However, poor operation and maintenance of these systems and provision of inadequate facilities for the disposal of saline drainage effluent resulted in limited overall success. The paper suggests that to ensure the sustainability of irrigated agriculture in the Indus Basin, technical and financial support is needed and enhanced institutional arrangements including coordination among different federal and provincial government agencies to resolve inter-provincial water allocation and water related issues is required. 相似文献
11.
P. Minderhoud 《Agricultural Water Management》1982,5(2):95-125
A model is presented that can be used to determine drainage measures and their costs. It has been elaborated for a wet tropical climate, for situations with open field drains, shallow groundwater table and a homogenous soil underlain by an impervious layer. The land is flat and the proposed agricultural use requires control of the groundwater table.A basic element of the model is a scheme to compute the water balance per day for a drainage parcel. Discharge, evapotranspiration, groundwater level and soil moisture storage are estimated as functions of rainfall, potential evapotranspiration, vegetation and soil characteristics and of an assumed drainage intensity. The water balance computation is performed for periods of 5–40 years of daily rainfall data, for a series of drainage intensities. The results can be subjected to a drainage criterion, from which a design drainage intensity and a corresponding drain spacing can be derived.Finally the layout of canals for a block of 4 × 1 km2 is determined and excavation and a series of canal characteristics are computed.A summary of some applications is included. 相似文献
12.
Assessing the groundwater dynamics and impacts of water saving in the Hetao Irrigation District, Yellow River basin 总被引：2，自引：0，他引：2
Water resources allocated to the agricultural sector in the Yellow River basin are being reduced due to severe water scarcity and increased demand by the non-agricultural sectors. In large-scale irrigation districts, the application of water-saving practices, e.g., improving the canal system, using water-saving irrigation technology and adjusting cropping patterns, is required for the sustainable agricultural development and the river basin environmental equilibrium. Adopting water-saving practices leads to lowering the groundwater table and to controlling salinity impacts related to excessive irrigation. However, assessing the effects of water-saving practices on the groundwater system requires further investigation. The Jiefangzha Irrigation Scheme of the Hetao Irrigation District is used as a case study for analyzing the temporal and spatial dynamics of the groundwater table. A lumped parameter groundwater balance model has been developed with this purpose and to assess impacts of various water-saving practices. The model was calibrated with monthly datasets relative to the non-frozen periods of 1997-1999 and validated with datasets from 2000 to 2002. Results indicate that canal seepage and deep percolation account for respectively 48% and 44% of the annual groundwater recharge. Groundwater discharge by direct evaporation and plant roots uptake represents 82% of the total annual groundwater discharge. After validation, the model was applied to assess the impacts of various canal and farm irrigation water-saving practices. It was observed that improvements in the canal system (e.g., canal lining, upgrading the hydraulic regulation and control structures, improving delivery schedules) might lower the groundwater table by 0.28-0.48 m, depending upon the level of implementation of these measures. Higher declines of the groundwater table are predicted when water-saving technologies are applied at both the canal and the farm systems. That decline of the water table favours salinity control and reduces capillary rise, thus reducing the groundwater evaporation and uptake by plant roots; that reduction may attain 128 mm. However, predictions may change depending on the way how water-saving measures are applied, which may be different of assumptions made; therefore, there is the need to perform a follow-up of the interventions in order to update predictions. Results indicate the need for appropriate research leading to improved irrigation management when the decline of the groundwater level will reduce groundwater contribution to vegetation growth. 相似文献
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《Agricultural Water Management》2006,83(3):243-251
Irrigation schemes have contributed to the availability of water not only for agriculture but also for domestic use by rural households. In the Uda Walawe irrigation scheme in southern Sri Lanka, irrigation canals are being lined with concrete to save water, meant to enable extension of the irrigated area. The effects of lining on the availability of water for multiple uses were investigated by field measurements of water levels and by an inventory of the perceptions of changed water availability by the population through focus group discussions. From the measurements it was determined that canal seepage provides an important contribution to groundwater recharge. It was estimated that after concrete lining the annual groundwater recharge in the irrigated areas will be reduced by approximately 50%. This saves a substantial amount of water that can be used to extend the irrigation area so more people can benefit from the available irrigation water. However, in the currently irrigated areas lining will have negative impacts by lowering groundwater levels due to a reduction in seepage from canals. This seepage contributes to the recharge of shallow wells used by the population to obtain water for drinking and cooking. The perception of the population was that enough water remains for domestic use. Other changes, such as reduced yields from home gardens were considered to be more important. Despite these negative impacts the expected positive impacts in the extension area justify, from a social equity point of view, concrete lining as a measure to redistribute the available water over the Uda Walawe area. 相似文献
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基于地下水均衡模型,分析了陕西泾惠渠灌区不同频率典型年的地下水均衡状况,结果表明降水入渗补给、渠系渗漏及田间灌溉入渗补给、井灌回归补给是灌区地下水的主要补给源,占总补给量的85.99%~82.89%;而人工开采是灌区地下水的主要排泄途径,农灌地下水开采量、人畜和工业用水开采量占总排泄量的69.7%~72.86%.以2010年为现状基准年,2020年为规划水平年,结合灌区发展规划,设置了4种不同的灌区发展情景模式,运用所建立的地下水均衡模型计算了不同情景模式下的地下水位埋深,其变化范围为0~0.07 m;以地下水位变幅最小为准则,得出了不同频率典型年合理的渠井用水比例范围为1.49~1.53,从而为灌区地下水资源的高效持续利用提供了依据. 相似文献
17.
Performance assessment of irrigation water management in old lands of the Nile delta of Egypt 总被引：1，自引：0，他引：1
Doaa E. El-Agha David J. Molden Ashraf M. Ghanem 《Irrigation and Drainage Systems》2011,25(4):215-236
This paper provides the methodology and results of a cross-scale diagnostic performance assessment program of the irrigation water management in the old lands of the Nile Delta of Egypt. The analysis was done at three levels; main canal level, branch canals level and on-farm level of the Meet Yazid command (82,740 ha) for the year 2008?C2009 to highlight areas for improvement. At the main canal level the annual average percentage of irrigation water returning to drains and groundwater was 53% of the total water supplied. Since Meet Yazid lies at tail end of the delta, and there is groundwater salinity, opportunities for reuse are increasingly limited moving north to Lake Burullus. This would indicate opportunities for real water savings. The results of monthly relative water supply of the main canal indicated mismatch between demand and supply especially during the winter months, and when supply is low farmers do reuse drainage or groundwater. Also, the assessment of the three branch canals showed non-uniformity of water distribution and mismatch between demand and supply even when comparing improved and non-improved canals. At the on-farm level in paddy fields, the amount of irrigation flows to drains and saline sinks varied from 0.46 to 0.71 of inflow. In spite of these values of non-uniformity and low depleted fraction, the relative evapotranspiration (ratio of actual to potential) evaporation was uniformly high, indicating most crops of most farmers were not water stressed, which is also confirmed by the high yield values. The average values of productivity per unit water depleted by ETact were 1.04 and 1.05 kg/m3 for rice and wheat fields, respectively, with yields of rice and wheat at 8 and 6 t per ha respectively. On farm and tertiary improvements alone will not yield real water savings, as excess water in the main canal and drains will continue to flow out of the system. Rather the focus should first be on supplies to the main canal, accompanied by more precise on farm and water delivery practices at branch and tertiary levels, and ensuring that environmental flows are met. There is an added advantage of focusing on this tail end region of Egypt that this response would lessen vulnerability to reuse of polluted and saline water. 相似文献
18.
大中型灌区干渠输配水渗漏损失经验公式探讨 总被引：10，自引：0，他引：10
中国广泛使用考斯加可夫经验公式来估算渠道输水渗漏损失，在渠道实际运行中，存在一些缺陷，为此，根据Davis-Wilson公式，并考虑使用的习惯性和方便性，建立了渠段输配水损失与渠道断面尺寸，水力条件，土壤类型，地下水埋深等因素相关的经验公式，同时将渠道衬砌等其他所有因素一并考虑在渗漏折减系数中，并建议采用实测方法来估算该系数。 相似文献
19.
The Zawia and Mansour irrigation areas, formerly part of Lake Burullus, were reclaimed, drained and developed in the 1960's. Reclamation was not fully successful, however, and the agricultural land is still highly saline. Recent studies carried out on behalf of the Executive Authority for Land Improvement Projects by Euroconsult and the Study and Design Department of the Authority concluded that the groundwater tables were still too high and that the drainage should be intensified and deepened. The question remained whether, and to what extent, improved drainage would increase seepage from the lake into the polder area. The studies reported here showed that geohydrological conditions were such that no seepage of importance can be expected. Piezometer observations of vertical pressure gradients confirmed these results. Calculations showed that an increase in seepage due to improved drainage would be very small compared with the capacity of the existing drainage system. 相似文献
20.
Modelling surplus canal water releases for artificial recharge of groundwater through surface drainage systems 总被引：1，自引：0，他引：1
Intensive agriculture in various countries has resulted in over-exploitation of groundwater resources leading to a decline
in the water table. Artificial groundwater recharge offers a good method of preventing the water table from declining further.
The Indo-Gangetic plain is currently facing the problem of a declining water table. The network of surface drains constructed
to control previous waterlogging could now be used for recharging groundwater with surplus canal water during the low irrigation
requirement period, as most of the drains cut across the irrigation canals. Therefore, a model was developed to determine
the optimum discharge to be released at the head of each drain under natural flow conditions and with interruption in the
flow by providing check structures across the drains at suitable intervals. In the proposed method, water is released in such
a way that outflow becomes zero at the outfall of the drain. The results obtained reveal that the strategy developed could
be adopted for recharging the declining water table through surface drainage systems.
Received: 3 February 1999 相似文献