西北干旱区绿洲不同灌溉制度的数值模拟

运用耦合了包含土壤－植被－水文－积雪参数化的陆面过程的非静力平衡中尺度模式MM5，将水平分辨率提高到1km，在“我国西北干旱区绿洲不同水量灌溉对环境影响的数值模拟”一文的基础上，通过数值模拟的方式，运用保持土壤体积含水量稳定的方法确定灌溉制度的方法研究了我国西北干旱区绿洲7月下旬在不同灌溉制度滴灌下土壤、径流与近地层大气的不同变化状况。结果表明：1. 当按50m³/hm²/天的水量进行隔天灌溉，或隔4天灌溉一次，土壤体积含水量不能保持稳定，需要补充灌溉才能保证其稳定，所以这样的灌溉制度不适合于7月下旬的河西绿洲。2. 均匀施灌10天，每天施灌50m³/hm²；施灌5天，隔一天施灌100m³/hm²，以及隔4天施灌一次，每次灌水250m³/hm²这三种灌溉制度中，前者形成的径流最小，土壤湿度变化幅度也最稳定，所以是最优的灌溉制度。但是现实生活中由于设备、人力等一系列客观条件限制，每天平均施灌的灌溉制度难以实现，可以采取相近的灌溉制度，如隔天施灌，尽量缩短两次灌溉间隔时间，每次所需的灌溉量很小，使得滴灌水量最大程度地转化为土壤水，减少地表径流的产生。所以说，为了不造成水资源的浪费，应该在选取合适灌溉水量的基础上，依合理的施灌制度进行灌溉，这样的水其利用率会比较高，达到节水灌溉的功效，从而为干旱区节约有限的水资源。

Numerical Simulation of Different Irrigation Scheduling on Oasis in Northwest China

The variation of energy and water exchange between land surface and atmosphere, the influence on atmospheric temperature and humidity at 2m height, soil moisture at four layers (10cm, 30cm, 60cm, 100cm)， and surface/underground runoff under different irrigation schedule from 20 July to 30 July, 2002 were analyzed on oasis in arid region of NW China and simulated using the non-hydrostatic atmospheric mesoscale model MM5, in which the land surface process parameterization (OSU LSM) was involved and soil layers, vegetable layer, hydrological process and snow were included. The horizontal resolution was selected as 1km. We knew from “Numerical simulation of Oasis’ Environmental influence under different quantity irrigation in arid regions of Northwest China” that 500m³/hm²/10d is a proper volume for later dekad of July,2002. We determinate the best irrigation schedule based on the method of keeping soil moisture steady. The results showed that: firstly, soil volumetric water content fell down gradually when irrigating 50m³/hm²/d every two days or every several days. Soil moisture could not keep in a stable range, and could not provide steady water supply for the plant growth. So this irrigation schedule is not a proper one for later dekad of July in oasis. Secondly, the surface runoff of irrigation schedule is smallest when irrigating ten days evenly and the quantity is 50m³/hm² every day. Soil moisture variation of it is smallest also among the following three schedules: irrigating ten days, and 50m³/hm², every day; 100m³/hm²/d, every two days; and 250m³/hm²/d, every five days. So the first schedule is the best scheduling according to the irrigation schedule determination method from soil moisture maintenance. But it is difficult to realize because of a series of problems such as equipment and labors. Then, the most similar schedule can be adapted in real life. In one word, the shorter the interval between irrigations under the given irrigation quantity crops need every time, the better. So the irrigation water can be transformed to soil moisture as soon as possible to supply crops on it, not to flow down along the slope of topography as surface runoff. So we’d better irrigate as the best irrigation schedule so as to hold the limited water resources.