西北旱区绿洲农业灌溉条件下水资源转化模型及其应用研究

It is of great importance to study on the hydrologic cycle and the transformation law of water resources for the efficient utilization of water resources and the improvement of fragile ecological environment. This program is on the background of water scarcity, groundwater drawdown and ecological deterioration in the arid oasis of northwest China. This study will follow the profound understanding of the transformation law among irrigation water (precipitation), soil water and groundwater, and of the water cycle variation along with the development of irrigation farming in the oases. Numerical simulation method will be used for quantitative revealing the relationship of canal seepage and groundwater recharge. Based on the land use situation and the spatial distribution of canal system, the water resources transformation model for regional scale will be established to study the transformation law of water resources in the typical region, focus on analyzing the transformation relationship of water resources for cropland and canal system considering the water delivery process under natural condition. Moreover, the simulation and prediction of the water cycle process for regional scale will be conducted under the conditions of different farming activities. Finally, the environment-friendly cropping structure and the utilization mode of water resources are obtained in the arid oasis. The objective of this study is to establish a water resources transformation model for regional scale which can accurately describe the transformation process of water resources, aim to answer to below two scientific questions, i.e. how farming activities influence the water cycle process for regional scale in the arid oases? How to quantify the transformation relationship of water resources? This study can provide a scientific evidence for the reasonable development, utilization and allocation of water resources, and a decision basis for the government.

研究流域水循环与水资源演变规律，对于促进水资源持续高效利用、改善脆弱的生态环境具有重要的现实意义。本项目以我国西北旱区绿洲水资源短缺、地下水位下降和地表生态恶化为背景，以深刻认识灌溉水（降水）、土壤水和地下水转化规律及绿洲灌溉农业发展对流域水循环过程的影响为主线，采用数值模拟方法，揭示渠道渗漏水对层状包气带及地下水补给的定量规律，建立考虑土地利用状况和渠系空间分布的区域尺度水资源转化模型，研究典型区域水资源转化规律，重点分析农田水分转化关系和考虑行水过程的渠系水分转化关系，并对不同农业活动条件下区域水循环过程进行模拟预测，获得面向环境友好的作物种植结构和水资源利用模式。本研究旨在建立能够准确描述干旱区绿洲水循环过程的区域水资源转化模型，力求回答"干旱区绿洲农业活动如何影响区域水循环过程？其定量关系是什么？"等科学问题，为干旱绿洲区合理开发、利用和配置有限的水资源提供科学依据和决策支持。

水资源是干旱区绿洲的生命线，石羊河流域是我国缺水最为严重及生态环境最为脆弱的地区之一，优化目前流域内的水资源利用方式和缓解地下水位下降速度势在必行。开展水文循环和水资源转化的过程与规律研究，对合理开发、利用和配置干旱区有限的水资源具有重要的现实意义。本文以石羊河流域武威盆地为例，开展了武威盆地水资源转化关系的相关理论和模型模拟研究。.1、利用HYDRUS-2D对不同防渗措施下渠道的渗漏过程进行了模拟分析。结果表明，模拟的累积入渗量与实测值基本吻合，说明HYDRUS-2D在模拟渠道渗漏过程方面具有一定的可靠性。选定武威盆地内典型的总干渠、干渠和支渠，采用HYDRUS-2D对每年实际过水情况下不同土壤质地和不同类型的混凝土衬砌渠道渗漏过程进行模拟分析，确定渠系入渗补给地下水比例，结果表明武威盆地河灌区渠系入渗补给系数约0.67，井灌区渠系入渗补给系数约0.55。. 2、结合CROPWAT模型和Thornthwaite-Mather（T-M）模型，构建了武威盆地农田作物根区水均衡模型，研究了农田作物根区水资源转化关系。结果表明，农田作物根区补给水量（降水量与灌溉量之和）与消耗水量（蒸散发量与深层渗漏量之和）基本相等，说明基于CROPWAT模型和T-M模型在模拟根区土壤水平衡方面是值得信赖的，根区以下深层渗漏量与补给水量（降水量与灌溉量之和）的比例在0.17-0.26之间，且随着补给水量的增大而增大。农田蒸散发量占补给水量（降水量与灌溉量之和）的比例在0.69-0.78之间。. 3、构建了武威盆地Molden-Sakthivadivel（M-S）水均衡系列模型，包括武威盆地地表农业区域水均衡模型、武威盆地地表区域水均衡模型、武威盆地地下水区域水均衡模型及武威盆地整体水均衡模型，研究了武威盆地水资源的转化和消耗规律。结果表明农田蒸散发量是武威盆地最主要的水分消耗项，占总消耗量的56%-64%，武威盆地水量平衡的计算结果比较真实的反映了武威盆地实际的水量转化关系，说明M-S水均衡计算模型在计算武威盆地水量平衡方面具有一定的可靠性。