Research And Practical Application On Distributed 3D Water-Salt Transport Model In Arid Oasis Area

Implementing water resources comprehensive assessment, there is a need to carry out simultaneously assessment of surface water resources and groundwater resources, and assessment of the quantity and quality of water. Similarly, allocating reasonably water resources, there is a need to allocate conjunctive surface- and ground-water. And allocating quantity of water, there is a need to consider the different requirement of quality of water for different user. In order to meet above needs, based on analysing the features of salt transport & utilization and transformation of water resources in arid oasis area, a distributed 3D water-salt transport model called Water-Salt Balance Process for MODFLOW-2005 (MF2005-WSB) was developed for arid oasis area. MF2005-WSB centered on calculating the consumption of water and united to simulating surface- and ground- water-salt. And then, in case of Yanqi basin, it was studied on the practical application of MF2005-WSB.In this research, an arid oasis area was divided into three kind of calculation cell, which are irrigation cell, town-country cell and ecology cell. And then, two packages called respectively Farm Consumptive Use Package (FRM) and Off-farm Consumptive Use Package (OFM) was developed for calculating the consumption for different kind of calculation cell, which adapted to the basic framework of modular design concept of MODFLOW (Modular Three-dimensional Finite-difference Groundwater Flow Model). Those above packages were integrated into the Arid Oasis Consumptive Use Process (OCU) related to the source/sink terms of Ground-Water Flow Process (GWF). According to the basic principles of water-salt balance, the Water-Salt Balance Process (WSB) was developed coupling some relative variables of the FRM, OFM, the Streamflow Routing Package (SFR), Multi-Node Well Package (MNW) or Well Package (WEL), and Ground-Water Transport Process (GWT). The main body of MF2005-WSB combined with the GWF, GWT, OCU and WSB. Because of the particularity of the water cycle and salt transport of Lake Bosten, a water-salt control model for lake with both inflow and outflow was developed, which can adjust to the Lake Bosten. In view of the complicated pre- and post-process for the data of the MF2005-WSB, it explorative studied on the obtaining and processing method of data based on 3S technology (Remote Sensing, RS; Geographic Information System, GIS; and Global Positioning System, GPS).According to the practical application of this model in plain oasis area of Yanqi basin, some conclusions were drawn as follows: (1) After analysing the inter-annual variation feature of the main river runoff in Yanqi basin using the hydrological wavelet analysis method, the Kaidu river have four main periods of runoff, which are 6a, 10a, 15a and 38a; the Huangshuigou river and Qingshuihe river have two main medium-short term periods of runoff, which are 10a and 6a. (2) In recent years, the ecological water consumption is about 31% of the total water consumption of the oasis area in Yanqi basin; In the perspective of the benefit of the social development and the environmental protection, the water and land exploitation had saturated excessively in oasis area in the current, and exceeded the bearing capacity of water resources; It is not suitable to expand the area of cultivated land. And the current situation of land use can be maintained barely. (3) In view of suitable ecological water table (the depth of groundwater table is 2-4m), because the development and utilization of groundwater is in a very low degree, the depth of groundwater is generally lower than 2m in the oasis farm region; But, the depth of groundwater is generally more than 5m in the nonagricultural region where the recharge of groundwater were lead to decreasing due to slightly high ratio of channel anti-seepage; Therefore, it is very necessary to mining prior groundwater for agricultural irrigation. (4) In the condition of implementing the short-term planning in Yanqi basin, the total water quantity importing to Lake Bosten can increase. If both the water division proportion of the Baolangsumu hub and the water quantity exporting to Lake Bosten can be reasonable controlled, the water level of Lake Bosten will be run at safety water level, and the water quality of Lake Bosten will be improved year by year. (5) It is beneficial to water environments of Lake Bosten when the construction project in the near future was completed in Yanqi basin. And water environments of Lake Bosten would tend to a well-ordered circle.