农业工程学报
農業工程學報
농업공정학보
2015年
2期
94-101
,共8页
李山%罗纨%贾忠华%潘延鑫%武迪%张登科
李山%囉紈%賈忠華%潘延鑫%武迪%張登科
리산%라환%가충화%반연흠%무적%장등과
模型%水分%盐分%反渗%DRAINMOD模型%水盐平衡%排水沟
模型%水分%鹽分%反滲%DRAINMOD模型%水鹽平衡%排水溝
모형%수분%염분%반삼%DRAINMOD모형%수염평형%배수구
models%moisture%salts%sub-irrigation%DRAINMOD%salt and water balance%drainage ditch
因干旱和半干旱下游灌区地势较低，排水出路不畅，排水系统往往成为承泄区外来水（上游灌溉退水和排水）的蓄水场所，使排水沟水位高于农田地下水位，反渗补给农田地下水，作物利用部分排水以后，如何维持农田良性的水盐平衡成为下游灌区一个迫切需要解决的科学问题。该文基于农田水盐平衡原理，以陕西一半干旱区下游灌区为例，在实测资料的基础上，首先利用田间水文模型DRAINMOD模拟了排水沟蓄水条件下，农田水位变化情况，然后计算分析了农田与排水沟的水盐交换关系。结果表明：在一个完整的种植年内单位长度排水沟上累计承接区外来水量为9.3 m3，减去流出水量，累计蓄积区外来水量为5.5 m3，农田单位面积上反渗累计补给田间地下水量为49.2 mm；累计农田排水量仅为2.3 mm。与作物蒸散发相比，现状条件下补给量虽然较小，但对维持和补给农田地下水起到了一定的作用。所产生的补给作用虽然增加了排水沟内盐分向田间地下水中的运动，但作物利用地下水过程中根区没有出现严重的盐分累积，对田间地下水盐分浓度影响也不大。所以，通过合理调控措施，充分利用区外来水，可以提高水资源利用效率。但排水系统长期运行条件下，高水位对农田水盐平衡的影响尚需进一步研究。
因榦旱和半榦旱下遊灌區地勢較低，排水齣路不暢，排水繫統往往成為承洩區外來水（上遊灌溉退水和排水）的蓄水場所，使排水溝水位高于農田地下水位，反滲補給農田地下水，作物利用部分排水以後，如何維持農田良性的水鹽平衡成為下遊灌區一箇迫切需要解決的科學問題。該文基于農田水鹽平衡原理，以陝西一半榦旱區下遊灌區為例，在實測資料的基礎上，首先利用田間水文模型DRAINMOD模擬瞭排水溝蓄水條件下，農田水位變化情況，然後計算分析瞭農田與排水溝的水鹽交換關繫。結果錶明：在一箇完整的種植年內單位長度排水溝上纍計承接區外來水量為9.3 m3，減去流齣水量，纍計蓄積區外來水量為5.5 m3，農田單位麵積上反滲纍計補給田間地下水量為49.2 mm；纍計農田排水量僅為2.3 mm。與作物蒸散髮相比，現狀條件下補給量雖然較小，但對維持和補給農田地下水起到瞭一定的作用。所產生的補給作用雖然增加瞭排水溝內鹽分嚮田間地下水中的運動，但作物利用地下水過程中根區沒有齣現嚴重的鹽分纍積，對田間地下水鹽分濃度影響也不大。所以，通過閤理調控措施，充分利用區外來水，可以提高水資源利用效率。但排水繫統長期運行條件下，高水位對農田水鹽平衡的影響尚需進一步研究。
인간한화반간한하유관구지세교저，배수출로불창，배수계통왕왕성위승설구외래수（상유관개퇴수화배수）적축수장소，사배수구수위고우농전지하수위，반삼보급농전지하수，작물이용부분배수이후，여하유지농전량성적수염평형성위하유관구일개박절수요해결적과학문제。해문기우농전수염평형원리，이협서일반간한구하유관구위례，재실측자료적기출상，수선이용전간수문모형DRAINMOD모의료배수구축수조건하，농전수위변화정황，연후계산분석료농전여배수구적수염교환관계。결과표명：재일개완정적충식년내단위장도배수구상루계승접구외래수량위9.3 m3，감거류출수량，루계축적구외래수량위5.5 m3，농전단위면적상반삼루계보급전간지하수량위49.2 mm；루계농전배수량부위2.3 mm。여작물증산발상비，현상조건하보급량수연교소，단대유지화보급농전지하수기도료일정적작용。소산생적보급작용수연증가료배수구내염분향전간지하수중적운동，단작물이용지하수과정중근구몰유출현엄중적염분루적，대전간지하수염분농도영향야불대。소이，통과합리조공조시，충분이용구외래수，가이제고수자원이용효솔。단배수계통장기운행조건하，고수위대농전수염평형적영향상수진일보연구。
Many downstream irrigation areas are constructed with drainage ditches to prevent the potential threat of soil salinization; but the irrigation water supply to these areas can rarely be guaranteed due to their disadvantage of being located far away from the water source. It is critical for local agricultural development and environmental protection to find practical water management practice for crop production in these downstream irrigation areas. In this paper, we present an analytical study on salt and water exchange between drainage ditches and the farmlands in a downstream irrigation area, where the drainage ditches were periodically filled with a large amount of inflow (irrigation return flow and drainage water) from the upstream irrigation area. Due to its low elevation and poor drainage outlet of the study area, the drainage ditches originally built for salinity control now capacitate water storage for crop fields in the growing season; the high water level in the drainage ditches produced sub-irrigation effect on crop fields to meet some crop water requirement. To investigate the effect of reduced drainage intensity on salt and water balance in the crop fields, we employed the field hydrology model – DRAINMOD to predict the field water table fluctuations under subirrigation condition based on observed data from summer 2009 to fall 2010. Salt and water exchange between crop fields and drainage ditches was then calculated based on the predicted water table variations. The results showed that the water table depth in the study area was generally below 2 m, while the water level in the drainage ditches was generally higher; the salinity level in drainage ditches was much lower than the groundwater in the crop fields. The water table depth predicted by the DRAINMOD model agreed with the field measurements reasonably well; the average deviation was 3.29 cm, the mean absolute error was 8.6 cm, and the correlation coefficient was 0.97. With DRAINMOD simulations of water table depths in the crop fields and the measured water level changes in the drainage ditches, we calculated salt and water exchange between drainage ditches and the subirrigatd fields; the results showed that in one planting year, the drainage ditches received a total inflow water volume of 9.3 m3 per unit length; while considering the outflow from the drainage ditches, the net ditch storage was 5.5 m3 per unit length per annum. The calculated subsurface drainage was only 2.3 mm while the cumulative subirrigation water depth was 49 mm during the study period; subsurface drainage occurred only occasionally during some heavy rain and irrigation time period, the drainage ditches provided subirrigation to crop fields during the rest of the time due to the periodic inflow from the upstream irrigation area. Comparing with the crop evapotranspiration, the subirrigation water amount was relatively small, but the heightened water level in the drainage ditches reduced drainage intensity, resulting in less subsurface drainage in the growing season. The high water level in drainage ditches had positive effect on recharging the water table of the farm fields. The calculated salt load moved into fields with the subirrigation water was about 20 times of that lost with the subsurface drainage discharge, but the actual salinity in the field was much lower than the salt tolerance level of cotton, no significant salinity buildup was observed in the soil profile. Currently, the inflow from the upstream irrigation area had no negative impact on salt and water balance in the study area; instead, it alleviates the draught stress in the downstream irrigation area. The long-term effect of maintaining high water level in the drainage ditches on salt balance in the crop fields, however, needs further investigation.
