Irrigation Scheduling Optimization for Ecological Security Water and Eco-Environment Relationship

Water is a key factor for the ecological health and social development of irrigated oases in Northwest China. The change of irrigation water will break the water cycle pattern, may affect food production and ecological stability, and even lead to ecological problems such as wetland shrinkage and vegetation degradation. Hetao irrigation area is the largest first irrigation area in Asia, with an effective irrigation area of 8.61 million mu, but the average annual rainfall is only 168mm. How to coordinate the ternary goal of irrigation water, food security and ecological health is not only a practical problem, but also a common challenge for arid irrigated oases in Northwest China. For the irrigated oasis of outflow River in arid area, the big difference between outflow River and inland river is that the water source of outflow river is relatively sufficient and plays a leading role, with local water resources as auxiliary. The ecological water use problems caused by the development and utilization of water resources in such areas are more significantly affected by man-made, and the transformation process between surface water and groundwater is also very complex. The overall mode is: the external water is transported to each area of the oasis through the multi-level artificial canal system, and the groundwater along the way is replenished to meet the water demand for crop irrigation. At the same time, it also supports the ecological water use of forests, grasslands, lakes and wetlands outside the farmland. The groundwater responds very significantly to the amount of water diversion. Excessive water diversion or excessive water saving will directly lead to the rise and fall of groundwater level in the oasis, and even affect the oasis vegetation ecology and river lake balance. In order to protect the benign development of water cycle ecological effect in the oasis area, the core issue of water resources ecological security is to maintain a certain groundwater level, which is reflected in the balance of groundwater supply and discharge in an appropriate range. The purpose of this study is to analyze the water-yield-ecology response relationship by means of multiple remote sensing data-set, and optimize irrigation scheduling considering the food production, water consumption control and ecological security. To this end, we choose Hetao Irrigation District located in Inner Mongolia as study region. First, we establish remote sensing based model to estimate plantation structure, crop water consumption, food production, and surface soil salinity by multi-sensor satellite data. By long term estimation of water cycle element and groundwater level over 15 years, the study analyze the response relationship of crop water consumption and food production to groundwater level and salinity based on different inflow conditions. Based on the ecological sensitivity of typical crop types of water and food production, a dynamic optimization method of irrigation scheduling targeting shallow groundwater area is proposed, and the water-saving and production-increasing effect is tested.