Drastic model application to groundwater vulnerability elucidation for decision making: the case of south western coasta
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ORIGINAL ARTICLE
Drastic model application to groundwater vulnerability elucidation for decision making: the case of south western coastal basin, Ghana Robert Kofi Yankey1,2,3 · Geophrey Kwame Anornu1,2 · Shiloh Kwabena Osae3 · Samuel Yao Ganyaglo3 Received: 13 August 2020 / Accepted: 17 October 2020 © Springer Nature Switzerland AG 2020
Abstract The health of the population is intertwined with the availability and supply of potable water. With many people around the world resorting to groundwater resources as a source potable water supply, it becomes imperative that the state of groundwater susceptibility to contamination is known. The DRASTIC model has been applied to determine the state of aquifer vulnerability to contaminants. The seven hydrogeological parameters were considered in the standard model and the resulting vulnerability, DI were classified into three vulnerability zones; low, moderate and high. The model was then modified to include land use/land cover (LU) and lineament density (LIN) parameters and net recharge (rm). The modified vulnerability indices were designated as DI-LU, DI-LIN, DIrm and MDI (combined modification). The results revealed the land area under high vulnerability under DI, DI-LU, DI-LIN, DIrm and MDI were 32.2, 26.2, 33.7, 26.2 and 40.4% respectively. There were no significant difference between the standard moderate vulnerability class and the modified derivatives (DI + LU, DI + Lin). The combined modification (MDI) however led to 17% decrease in this class of vulnerability. The model was validated using a nitrate concentration of 36 samples collected for the purpose. The validation assessment revealed that the performance of the model was improved with modification. Keywords DRASTIC model · GIS · Groundwater · Vulnerability index · Lineament · Land use/land cover
Introduction Groundwater is chief source of freshwater reserve in the world. Increasingly it’s becoming a source of choice in several portions of the world. It has found use in domestic, agriculture and industry for purposes such as drinking, irrigation, and manufacturing. It is estimated that 50% of potable water used in France, 70% in China and 45% in Ghana come from groundwater, (Buamah et al. 2008; Tai et al. 2012). This is partly due to the contamination of surface water. Furthermore, the need for freshwater supply sources is likely to rise due to population pressures. This phenomenon will * Robert Kofi Yankey [email protected] 1
Regional Water and Environmental Sanitation Centre, Kumasi, Ghana
2
Civil Engineering Department, College of Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
3
National Nuclear Research Institute, Ghana Atomic Energy Commission, Accra, Ghana
be profound in the third world where physical development outpaces water supply infrastructure. People would turn to groundwater because the saturated zone houses twentyone percent (21%) of the world total freshwater and about ninety-seven (97%) of the world unfrozen freshwater (Dunne and Leopold 1978
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