Study On The Suitability Assessment Of Sites For Direct Injection And River Infiltration Of Reclaimed Water For Groundwater Recharge

Reclaimed water recharge is an effective way to alleviate regional waterresources crisis. The current situation of China’s reclaimed water recharge wasinvestigated by conducting field surveys in some typical cities. By comparativeanalysis on the impacts of site characteristics on the recharge projects under differentrecharge modes, the basic information about recharge fields were collected in sometypical cities to provide site indexes for the suitability assessment system of reclaimedwater recharge. Then, the procedure of establishing suitability assessment system ofrecharge sites for reclaimed water is described. The assessment criteria for directinjection and river infiltration are concluded according to the respectivecharacteristics. The assessment systems for these two recharge modes are built andapplied in the practical evaluation. The detailed conclusions are as below:1) At present, there are three recharging modes of reclaimed water in China,including farmland irrigation, direct injection and river infiltration. The siterequirement for different recharge modes are different. The characteristics of the fieldsthat are suitable for the farmland irrigation are summarized as high protective abilityof vadose zone and deep groundwater depth. The characteristics of fields that aresuitable for direct injection are summarized as poor infiltration through surface,coarse and well connected aquifer media, and deep groundwater depth. Thecharacteristics of fields that are suitable for river infiltration are summarized as deepgroundwater depth, high permeability of riverbed and high protective ability ofvadose zone.2) Based on the respective characteristics of direct injection and river infiltration,the site suitability assessment systems for these two recharge modes are builtaccordingly. The selected9indexes of direct injection are mainly fromhydrogeological conditions, quality of underground water, economic indicators, andenvironmental indicators. For river infiltration, there are12indexes included, mainly from riverbed infiltration capacity, hydrogeological conditions, quality ofunderground water, economic indicators and environmental indicators. After selectionof the indexes, the quantitative classification and rating weight calculation areperformed for all indexes of these two different recharge modes. At last, theassessment systems of recharge sites suitability for reclaimed water are built based ondifferent recharge modes.3) By applying the site suitability assessment system of direct injection inGaobeidian direct injection site, it can be found that this site is moderately suitable forreclaimed water recharge, and to take reasonable recharge schedule is also needed toavoid secondary disasters. By applying the site suitability assessment system of riverinfiltration in ChaoBai river-the project YinWenJiChao river infiltration site, it can beseen that this site is moderately suitable for reclaimed water recharge, and it isnecessary to take some measures for river dredging to prevent the formation of thicklayers of silt on riverbed and the reduction of the river infiltration capacity.