Study On The Dual Control Of Groundwater Abstraction Amount And Table In Groundwater Over-exploitation Zones In Northwest China

Groundwater plays an important role as source,ecological factors and environmental factors in arid&semi arid inland river basins of Northwest China.The only method for the sustainable groundwater resources utilization and environmental conservation is to implement the groundwater total amount control and to preserve the groundwater table in a rational level.The establishment of groundwater dual control management system of abstracton amount and water level has become an important target for implementing the strictest water resources management in Northwest China.However,current research didn't pay much attention to the construction of technology system for duarl control indicators right now,which has restricted the implementation of dual control in Northwest China.This study introduced the scientific concept of groundwater resource evaluation and the reasonable principles of water resources management as foundation to design the indicators of groundwater abstraction amount and water leveldual control.Two types of indicators were set up,such as long-term dural contro indicators and annual dynamic dural contro indicators.The main management issue of long-term indicators need to be solved was to make a reasonable choice of different functional properties of groundwater.The main scientific issuewas to delinate the intrinsic link between water amount and table in long-time scale.The main management issue of annual dynamic indicators wasto predeteime annual amount and table index for assessment,and to improve the efficiency of index predetermination.Compared with long-term indictors,the added main scientific issue was to reduce the error of water level caud by by the uncertainty of annual hydrology.In order to solve the scientific and management issues,this research put forward a technology system for indicators deteremination.The main principle for long-term indicators determination was“water level priority”.The core technical in the technology system was groundwater numerical simulation modeling which can be used to deteremine the amount index under the constraint of water level index.The principle of“water amount priority”was proposed for the determination of annual dynamic indicators.The core technicals in the technology system were groundwater simulation modeling and surrogate model.The utilization of groundwater numerical simulation modeling can distinguish the influence of the annual hydrological uncertainty on the groundwater system.The application of surrogate modeling technology can simplify the numerical modeling process in determination of indicators and get the predetermined indicators rapidly to improve the efficiency of management.The technology system of the two types of indicators can solve both the scientific and management problems for corresponding time scale.The technical system was applied to the Minqin Basin in the lower parts of Shiyang River for example verification.Considering the difference in functions of resources,ecological and environmental,interval threshold for the long-term groundwater level index were determined.The calculated long-term groundwater amount index were6000×10⁴m³/a as lower threshold and 10000×10⁴m³/a as uppper threshold.The study area was divided into 13 groundwater allocation sub areas.The annual hydrological uncertainty condition was classified to three types as wet,flat and dry.The Kriging method and BP neural network as surrogate model of groundwater numerical simulation model were constructed to obtain the annual dynamic dual control indicators.The calculated predetermined groundwater abstraction amount index were10000×10⁴m³ under the dry hydrological scenario,8954×10⁴m³ under the flat scenario and 6390×10⁴m³ under the wet scenario.The calculated water table indiex of 2020were average water level increasing of 0.85m in wet scenario,average increasing of0.64m in flat scenario and average increasing of 0.55m in dry scenario.It can be concluded that the technology system was feasible through the typical application.The main innovation of this research can be concluded as follows:firstly,a concept was proposed for the first time that dividing the dural control indicators into long-term indexes and annual dynamic indexes,the concept clarified the scientific siginificance and managemt target of the dual control;secondly,the surrogate model of groundwater numerical simulation model was utilized as direct management tool in indicators determination,making the dual control management more scientific and operable and better promotion significance.