灌区控制排水条件下水盐调控及农田湿地盐分动态研究

发布时间：2018-03-12 12:49

本文选题：地下水利用　切入点：反渗　出处：《西安理工大学》2017年博士论文　论文类型：学位论文

【摘要】：农田排水系统是维持田间水盐平衡、保证作物正常生长的前提。但传统排水系统加快了土壤水分与养分的流失,不仅造成了接纳水体的污染,而且浪费了宝贵的水资源。农田控制排水在保留排水系统功能的同时,通过调整排水强度来提高水分利用效率,实现水资源的高效利用,降低排水对生态环境的不利影响。但是降低排水强度与控制土壤盐分之间存在一定的矛盾。本课题针对控制排水研究中存在的矛盾,以陕西省富平县卤泊滩盐碱地改良区为例,采用大田试验与模型模拟相结合的手段,研究了控制排水条件下农田水盐平衡及调控的关键技术,并分析了水文气象对控制排水洗盐的有利作用。主要研究成果如下:(1)监测结果显示,研究区因地势低洼,受区外来水补给,排水沟水位较高,利用DRAINMOD模型模拟分析发现:一个完整的种植年内单位长度(1m)排水沟累计承接区外来水量为9.3m~3,流出量为3.8m~3,排水沟单位长度上累计蓄积区外来水量为5.5m~3。计算累计地下排水量为2.3 mm,累计反渗补给量为49 mm;排水沟与农田之间的水盐交换是控制排水条件下水盐交换过程中的重要组成部分。(2)基于同一田块有、无作物种植2种情况下,地下水位差异是由作物对浅层地下水利用造成的这一假设条件,建立了大田作物浅层地下水利用量的计算模型。并利用监测数据进行了计算。结果表明,计算模型能够较好的反映田间的实际情况;在计算时段内,作物利用浅层地下水量为305.8 mm,相当于0.64mm/d;其中,棉花生长观测阶段对地下水向上补给量约160 mm,约占其总需水量的24%。(3)基于DRAINMOD模型和建立的降雨淋洗模型,分析了不同地下水控制埋深下棉花根区盐分变化;结果表明:在控制埋深为1.2 m时,在150 mm的淋洗灌溉量和降雨共同作用下,仅有少数年份根区土壤盐分含量超过了耐盐极限,淋洗保证率为87%;当控制埋深为1.5m时,不需要额外淋洗灌溉,依靠降雨淋洗即能够满足根区盐分的淋洗要求;以节水量为目标函数可知:控制埋深为1.5 m,平均补充灌溉为80 mm是研究区较为合理的田间水管理方案,与现状条件下理想的补充灌溉相比,直接节水量为140 mm。(4)基于平均假设建立了控制排水主要技术参数淋洗周期和淋洗水量的计算模型及控制排水决策体系,并通过试验数据进行了计算。结果表明:现状条件下,研究区内水位埋深为2.1m,1.5 m和1.2 m时,淋洗周期分别为＞194,140和119天;所需淋洗水量分别为0,82.6和94.1mm;与无地下水利用相比,节水量分别为0.47,1.53和0.91 mm/天,表明三种控制排水方案均可行,但控制埋深为1.5 m时节水量最大。若将地下水位从现状2.1m升至1.5 m,整个生长季可节约水量为85 mm。(5)针对控制排水限制了排水沟盐分输出,可能会对农田湿地产生危害的问题,建立了农田湿地水盐平衡模型。分析结果显示,现状排水条件下,湿地系统水量排出比为0.42,达到稳定状态时间约为4年,稳定时的湿地盐分浓度约为5.74 g/L,湿地系统能够健康运行,但排出比偏大,适宜的排出比应为0.25,系统达到稳态状态的时间为18年。采用该模型分析了控制排水方案(1.5m控制埋深,80mm灌溉)对农田湿地的影响,即使排出比为0,农田湿地系统也能健康运行,这说明,该排水方案不会对农田湿地系统产生不利的影响。综上所述,本文从排水和排水利用的角度出发,研究了干旱半干旱灌区控制排水措施过程中水盐交换及盐分累积过程,并分析了在不同控制排水埋深下灌溉节约水量和降雨淋洗作用,推求了控制排水关键技术参数的简化求取方法,决策体系和控制排水对农田湿地的影响。本文采用的方法可为控制排水措施的实施提供技术支持,研究区的研究结果可为相似灌区提供借鉴经验。
[Abstract]:The drainage system is to maintain the balance of water and salt, guarantee the normal growth of crops. But the traditional drainage system to speed up the soil moisture and nutrient loss, not only caused the acceptance of water pollution, and waste of valuable water resources. Farmland drainage control in retaining drainage system function at the same time, by adjusting the strength to improve drainage the water use efficiency, to achieve efficient use of water resources, reduce the adverse effects of drainage on the ecological environment. But the decrease between the drainage intensity and soil salinity control there is a certain contradiction. Aiming at the contradiction of controlled drainage in the research, taking Fuping County of Shaanxi Province lubotan saline land improvement district as an example, based on the field test the model and simulation method, studied the key technology of the control under the condition of drainage water salt balance and control, and analyzed the meteorological and hydrological control of the drainage of salt Good effect. The main research results are as follows: (1) the monitoring results show that the study area due to the low-lying land, the supply area of external water, high water drain, using DRAINMOD model analysis found that: a complete planting years per unit length (1m) drainage ditch outside the area to undertake the cumulative water volume is 9.3m~3, outflow for 3.8m~3, the drain on unit length of total accumulation water 5.5m~3. calculate the cumulative area of foreign underground drainage amount is 2.3 mm, the cumulative anti seepage recharge amount was 49 mm; between the salt water drains and farmland exchange is an important part of control condition of drainage water and salt in the process of exchange. (2) based on the same field no crops, 2 kinds of circumstances, the underground water level difference is the assumption that the crops on the utilization of shallow groundwater caused, established the calculation model of shallow underground water amount of field crops. It is calculated by using the monitoring data. Show that the model can reflect the actual situation of the field; in the calculation period, crop utilization of shallow underground water is 305.8 mm, equivalent to 0.64mm/d; the cotton growth stage to observation of groundwater recharge in about 160 mm, accounting for the total water requirement of 24%. (3) and the establishment of the DRAINMOD model rainfall model based on the analysis of different groundwater depth under the control of cotton root zone salinity; the results showed that: in the control of the depth of 1.2 m, 150 mm in the action of leaching irrigation amount and rainfall, only a few years of root zone soil salt content exceeds the limit salt leaching, guaranteed rate is 87% when the depth is 1.5m; control, without the need for additional leaching irrigation, depending on rainfall that can meet the requirements of root zone salt leaching; to save water consumption as the objective function that control the depth of 1.5 m, average 80 mm irrigation area is Field water management scheme is reasonable, compared with ideal supplemental irrigation under the present condition, the direct water amount was 140 mm. (4) model and drainage control decision-making system of main technical parameters of controlled drainage and leaching water leaching cycle is built based on the average assumptions, and calculated by experimental data. The results show that the present condition in the study area, the water depth is 2.1m, 1.5 m and 1.2 m, respectively, 194140 washing period and 119 days; the leaching water were 0,82.6 and 94.1mm; and no groundwater utilization compared, water-saving quantity is 0.47,1.53 and 0.91 mm/ days respectively, showed that three kinds of controlled drainage schemes are feasible, but control depth is 1.5 m. The maximum water season if the underground water level rose to 1.5 from the current situation of 2.1m m, the whole growth season can save water for the 85 mm. (5) for the control limit drain drain salt output, may have on the farmland wetland Against the problem, establish Wetland Farmland water and salt balance model. The analysis results show that the present drainage condition, wetland water discharged ratio is 0.42, reached a steady state for about 4 years, the wetland salt concentration when the stability is about 5.74 g/L, wetland ecosystem health, but the discharge ratio is too large, suitable discharge ratio is about 0.25, the system reaches steady state for 18 years. The model was applied to analyze the control drainage scheme (1.5m buried depth, 80mm irrigation) effect on farmland, even if the discharge ratio is 0, the farmland wetland system can run healthily, this shows that the drainage scheme will have adverse effects on the farmland wetland system. To sum up, this paper from the perspective of the use of drainage and drainage, the drainage control semi arid irrigation water and salt exchange process and salt accumulation process of drought, and analyzed in different depth of controlled drainage Under irrigation to save water and rainfall, calculate the simplified method of key technical parameters for drainage control, influence the decision system and controlled drainage on Farmland Wetlands. The method used in this paper can provide technical support for the implementation of the drainage control, the research results can provide reference for similar area.

【学位授予单位】：西安理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S276;S156.41

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