Groundwater Chemistry and Modeling of Aquifer Depth Around Uburu-okposi Salt Lakes, South Eastern Nigeria.


The study area comprised Uburu and Okposi towns in Ohazara Local Government Area, Ebonyi state and it lies between latitudes 60 00’N and 60 05’N, and longitudes 70 44’E and 70 50’E. The area belongs to the saline hydrogeological groundwater basin of Albian Asu River Group in Cross River Basin. Three major outcrops of saline groundwater in the study area are: Umuchime– Uburu lake, Ivu-Ezizo and Amaechi-Okposi lakes.

The saline lakes support long production of salts by rural women via local means. 20 water samples from the lakes, dug-wells and boreholes were analyzed to determine the hydrogeochemical constituents of the area. Values of total dissolved solids (TDS) in the samples range between 130 and 256,100mg/l. Calcium (Ca2+), magnesium (Mg2+) and sodium (Na2+) show significant concentrations of cations between 6 and 1440mg/l, 2 and 245mg/l and, 7 and 1231mg/l respectively.

Chloride is the most dominant anion and it ranges between 1000 and 1,153640mg/l. Total dissolved solids (TDS), chloride (Cl-) and calcium (Ca2+) concentrations are observed to be above objectionable limits for drinking water in the area. The chemical constituents revealed two saline groundwater types in the area; Ca-Cl and Mg-Cl waters. The Ca2+ and Mg2+ constituents generated hard water in the study area.

The calculated sodium absorption ratio (SAR) indicated depletion of sodium in the water and, as a result, the saline groundwaters are suitable for irrigation. Vertical Electrical Soundings revealed that the saline groundwaters with low resistivities are in the less permeable medium like clay, plastic shale and siltstone units. The best aquifers observed are the permeable sandstone units at the depth of 20m and fractured shale at 53m depth.


The study area comprised two towns-Okposi and Uburu in Ohaozara Local Government Areas, Ebonyi state (Fig.1.1). It lies between latitudes 60 00’ and 60 05’N and longitudes 70 44’ and 70 50’E. Uburu – Okposi is entirely underlain by Albian Asu River Group in Cross River Basin (Offodile, 2002) and it is located within Abakaliki brine fields in Lower Benue Trough (Tijani et al., 1996).

The existence of saline groundwater in the bedrock has made fresh water supply almost impossible. Individuals and the Ebonyi State Rural Water Supply Agency (EBRUWA) have drilled wells to remedy the water scarcity, but to no avail. Irrespective of the salt concentration, dwellers are using the groundwater for all purposes; drinking, domestic and for irrigation.

The target of this work is to use hydrochemical constituents analyzed from the water samples to infer the groundwater quality of the area, if it is above threshold, remedy can be suggested. Manifestations of this saline groundwater are at lakes Umuchime (Uburu town), Amaechi and Ivu-Ezizo (Okposi town). These lakes have long supported local salt production in the area.  


The origin of the dissolved salt in the groundwater of the study area may not have been properly ascertained. A lot of work has been done on hydrochemical and isotope characteristics of the saline waters of the area, e.g Loehnert (1982), Egboka and Uma (1986) and Tijani et al. (1996). The major problems in the study area are abandonment of many wells due to salty taste and non-prolific wells that dry up during dry season.

The salty taste emanates from the bedrock of the aquifer and the non-prolific wells are caused by false attempt to drill on the aquifer (shallow wells that end up on shale units). These cause water scarcity in the area. The situation is worst in dry season, people track for kilometers for the search of fresh water mostly for drinking.

In rainy season, the situation may be less because there will be salt dilution and recharge of the non-prolific wells by infiltration. Contributions are made from this research work by direct measurements (Vertical Electrical Soundings) around the salt lakes which could resolve the above-mentioned problems. 


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StudentsandScholarship Team.

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