HYDROGEOLOGY ENVIRONMENTAL GEOLOGY
Surface and groundwater resource exists in the study area but the interferences in planning and management cause water supplies to be scare. Many people, particularly the suburban dwellers buy water or fetch water streams, rivers and hand dug wells in the area.
Surface water bodies receive significant inflow as runoff for the greater part of the year, inspite the effect of evaportranspirition.
Egboka (1983) reported minor water falls due to fast flowing springs issuing from such boundaries of Ajali sandstone at the edges of Enugu-escarpment. The dominate dip ward flow along topographic highs has resulted in high surface flow velocity and often low stage of many rivers.
Water from Enugu coal mines mostly (Onyeama and Okpara mines) form a major source of pollution and contamination in rivers such as Ekulu and Nyaba in ENugu. The surface water bodies provide a major source of domestic water supply in most area, principally due to their accessibility.
SURFACE WATER IN ENVIRONMENTAL GEOLOGY
The study area is drained by Ekulu and Nyaba Rivers. Most of streams, having many tributaries are characterized by dentritic drainage pattern.
The streams rises high above sea level and flow through deep and V-shaped gullies incided in the superficial sands and the soft Ajali sandstone. Perennial streams rise from the middle level of the escarpment near the base of Ajali sandstone, both the valleys at the higher level are dry except for short periods during the rainy season.
The rain fall values were found to be 1,432m annually. The stream density is governed by two major factors. Firstly, the high humid conditions generate a considerable effective infiltration and secondly, the geology influences the drainage pattern. The water emerges from the Mamu Formation and mender on the impermeable Enugu shale through the joints some waters penetrates the Enugu shale.
At numerous points water gather to form perennial springs that emerge from the base of Mamu Formation of feed Ekulu, Nyaba Rivers and from other parts of the study area, the perennial springs from the base of the escarpment units and flows into Ekulu River and its tributaries as Asata and Emene Rivers.
The Ekulu River flows into the Nyaba River, which flows into the Idodo River, also outside the study area and finally into the Cross River.
The surface waters are most times polluted by sewage is from coal mine (Egboko and Uma 1985). Down ward flow of leachates also threatens groundwater quality. All these make them hazardous for drinking.
The flow of the rivers is much reduced during the dry season. Precipitation is lost by direct runoff of over land flow and water level is considerably increased in the streams and rivers during rainy season.
GROUNDWATER IN ENVIRONMENTAL GEOLOGY
Ground water is refered to as water found within the saturated voids beneath the ground. It involves the study of ground water and its relationship with the host rock. The general geology of the area control the occurrence and flow of ground water.
The Ajali sandstone and sandy members of the Mamu formation constitute the aquiferous unit .Within these formations various hydrologic units exist as perched water table, semi confined and confined aquifers. Borehole log records show that the aquifers are mostly sandy with clay and sandy shale as confining aquitards. The cyclic depositional patterns of the aquifer and aquitard units form multi-aquifer system of variable thickness and lateral extent.
GROUND WATER RECHARGE AND DISCHARGE IN ENVIRONMENTAL GEOLOGY
A recharge area is that portion of the drainage basin which the net saturated flow of ground water is directed away from the water atble.While the discharge area are the portion of the drainage basi in which the saturated groundwater is toward the water table.
The Mamu formation and the Ajali sandstone are recharging the study area .Recharge in the area , however occur as rainfall and lateral groundwater movement. Recharge occur mainly in the hillsand ridge underlain by latrites .The high level of water table fluctuation in the wells traping the latrites aquifer suggest high recharge .The sorted ground water is easily discharge , thus contributing to high stream flow.During wet season ,the surface runoff through the upper soil zone ensures that the wells are full of water.
As rain stops, the upper zones quickly dry out leaving the wells dried .Enugu area is located at the eascarpment which is more or less in a valley area while the high areas are made up of sandstone ( Ajali sandstone) which act as the recharging zone of water. As the rainfall drops at the high areas it percolates down to the subsurface. Thus ,the flow direction is towards the south(low land areas). It is discharging to the areas underlain by the Enugu shale.s
Engineering Geology In ENVIRONMENTAL GEOLOGY
The formation observed during my mapping were sandstone ,shale siltstone and coal seam ,but predominately sandstone.sandstone is a good for construction material but cannot with stand the rapid erosion in Iva valley.coal contain methane and it is flammable this has made construction on a coal terrain very difficult.