Optimum Water Wells Design for Nubian Sandstone Formations in Khartoum Bahri and Omdurman area (Kartoum State – Sudan)

Abstract

The ground water is the most important water resources in Sudan, recently the huge demand of groundwater in Khartoum Bahri and Omdurman area (Khartoum State – Sudan) increase due to the population and human activities increasing. Supplying and meeting these water needs for domestic, industrial and irrigation purposes subjected a huge problem to governmental bodies. Optimum water well designing is very important and represents a considerable urgent need for maximum well life and good water quality with low cost. For obtaining the optimum well design for Bahri and Omdurman area, the study followed three steps, many applications were done and the results were discussed. Firstly the lithology model for the Bahri area was created and other for the Omdurman area as well using Rock Works Software program for giving lithology description and aquifers nature for two areas. Then the water quality and hydrogeological conditions were evaluated for the lower aquifer (Nubian sandstone aquifer) for Khartoum Bahri and Omdurman area by constructing contour maps using an ARC GIS program. Lastly, these outputs (the aquifers nature and the hydrogeological information) were applied with the theoretical procedures for the well design to obtain the optimum well design for Khartoum Bahri area and Omdurman area. The study was concluded, there are two aquifers (upper and Lower) in Bahri and the same also upper and Lower in Omdurman area. The Bahri upper one has small thickness and not continuous. It includes Umm Ruwaba Formations and Superficial deposits and subject to pollution by sewage wells, therefore this aquifer must be sealed in designing the wells. The Omdurman upper one includes sand stone formations also subject to contamination due to sewage wells. The Lower one in Khartoum Bahri and Omdurman area is the Nubian sandstone aquifer and considers the main aquifer, the Omdurman lower aquifer is deeper than Bahri lower aquifer. From the Total Dissolved Solid (TDS) values of the lower aquifer in the two areas the Lower aquifer water is fit for drinking except the Elaolyab area in the Bahri and the south western part of the Omdurman area. Also in the two areas the lower aquifer water not corrosive according to the TDS and PH values, therefore the Mild steel casing is optimum for the Khartoum Bahri area and Omdurman area. The lower aquifer water in eastern and northern parts of the Bahri area is incrusting, and then a stainless steel screen with a large open area must be used in these areas to offset the effects of screen blockage. Also the Omdurman lower aquifer water is incrusting then a stainless steel screen with a large open area is the optimum for the Omdurman area to offset the effects of screen blockage. This study is recommended for obtaining optimum water wells design.