GROUNDWATER SALINITY IN SOUTHWEST OMDURMAN - SUDAN
BY:
MOHAMED GHABOUSH MAKI
: SUPERVISOR
MUNA MOHAMED OMER .rD
DISSERTATION SUBMITTED TO THE UNESCO CHAIR IN WATER
RESOURCES OF THE OMDURMAN ISLAMIC UNIVERSITY IN PARTIAL
FULFILLMENT FOR THE DEGREE OF MASTER (M.SC.) IN
WATER RESOURCES DEVELOPMENT AND MANAGEMENT
:
UNESCO CHAIR IN WATER RESOURCES
OMDURMAN ISLAMIC UNIVERSITY
September- 2005
Abstract
Groundwater salinity in Omdurman is noticified in Southwest region (study area) which lies between longitude 320 15` - 320 29` E and latitude 150 15` - 150 35` N. Salinity zones that impacted life in the area should be studied to draw attention to the problem size encounter the study area.
The objective of the study is to make a new map for salinity based on new samples analysis, investigate the problem size, link the problem with place and time and to suggest measures for well design.
The methods of the research used were, data collection, fieldwork for new data sampling and wells relocation in the area by GPS. Laboratories chemical analyses were curried for random water samples. The data were been sorted out to new table. Computer programs were used to evaluate and interpret the data.
The area is climatically arid to semiarid. From topographic point of view its characterized by broadly undulating topography interrupted by few scattered isolated hills of crystalline rocks and more frequent ridges and flat topped outcrops of sandstone, all partially covered by sand dunes and sand sheets. The ground surface slopes towards the east, with seasonal wadies and khours that drain toward the White Nile.
The general structure of geological column of the study area can be summarized as the recent alluvial deposits, tertiary volcanic deposits and upper cretaceous Nubian sandstone.
The aquifer of the area is sandstone units of Nubian formation with thickness of 250 – 300 m as upper aquifer and more than 400m as a bottom one. The top aquifer exists under unconfined to semi-confined aquifer conditions in the center and North of the study area. Semi confined and limited confined conditions prevail in lower aquifer Northwest and South of the area. The water depth in the upper aquifer ranges between 9 m – 73.9 m increasing Northeast indicating Northeast flow direction.
Hydraulic conductivity (K) ranges between 0.5 and 2m /h. Transmissivity (T) ranges from 40 to 160 m2/h for average thickens of 80m, and the storage coefficient (S) is in the range of 1 X 10 –2 and 1X 10 –4.
Hydrochemically, the new analyses show that the groundwater in the study area is generally of high salinity to very high salinity. There is no progress of salinity reduction in the area.
The results show that the water quality is becoming more worth for even boreholes close to the saline boundaries. Also for the exiting boreholes the quality of the water is changing (becoming more saline.). The dominant salinity ions in the area are Ca – Cl – SO4, Na – HCO3 – Cl, Na – HCO3 – SO4, and Na –Mg –HCO3 – SO4, Na –Cl –SO4 – HCO3, and Na Ca Mg – Cl SO4. Generally from the taste and chemical constituencies, the upper aquifer water in this area is not recommended for drinking purposes except in El salamania. The quality of the water is good for livestock. For irrigation however, it needs some technical guides where very high salinity water is detected.