Adjustment of Original DRASTIC model by means of Lineament Density to Map Groundwater Vulnerability: Case Study in Rania Basin, Kurdistan Region, Iraq

Abstract Groundwater has never been heavily relied on as a water source in Northern Iraq as it has been in the last two decades due to the rapid and often unplanned urbanization, industrial and agricultural projects. This paper attempts to present a concise groundwater vulnerability assessment of Rania basin to the local and regional planning authorities to ensure a more sustainable development in the area. The focus of the study is the Rania basin, which is a part of Dokan sub-basin in North East Iraq. The initial groundwater vulnerability assessment is mapped with standard DRASTIC model. It is then modified by adding “Lineament Density Index” to the original seven DRASTIC parameters due to the previously established close relationship between flow and yield of groundwater with lineament. The area is categorized into five vulnerability index zones of; very low (26%), low (32%), medium (31%), high (11%) and very high (0.012%). The modified model offeres a slightly different vulnerability classification of; very low (16.61%), low (35.45%), medium (30.32), high (17.57) and very high (0.05%). Measured Nitrate concentration is used to validate the assessment results. A progressive increase in nitrate concentration somehow reflects the different vulnerability zones identified by the DRASTIC models in the area. Samples of wet season show 15.96 mg/l, 17.68 mg/l and 20.1 mg/l for very low vulnerability, low vulnerability and medium vulnerability zones when classified by modified DRASTIC model.