Using computer systems to predict the changes in groundwater elevations due to recharge from rainwater harvesting

From the 19th century, the Bashiqa Region of Iraq has depended on groundwater for irrigation and domestic uses. Since 1980, many deep wells of small diameter have been drilled. This excessive water consumption caused a notable decline in groundwater level, which now lies more than 15 m below the ground surface. In consequence, nearly all the shallow large diameter wells have dried up. This present study introduces recharging aquifers using rain water harvesting techniques as a solution for this problem. A raster-based GIS was employed in conjunction with a surface runoff model that used a watershed modelling system (WMS) and a groundwater numerical model that used a finite-difference flow code (MODFLOW). The calibrated groundwater model suggested that four check dams should be employed to store rainwater at selected places where the infiltration ratio is very high. Model results indicate that after one year the check dams may raise groundwater elevations by more than 4.5 m at particular locations and generally by more than 0.2 m for the study area as a whole. Prediction of the expected elevations after five years suggested a continuing very positive effect on groundwater levels.