Ground Water

Ground water is used in:

• The Coastal Artesian Basin area
• The North West District
• Nearby hinterland districts
• The Rupununi Savannahs

The Coastal Artesian Basin aquifers are briefly described below.

The Coastal Artesian Basin occupies an area of about 7,500 sq. mi.. The axis of the basin (deepest part) coincides approximately with the alignment of the Berbice River. The sediments in the Basin achieve a maximum thickness of about 6,000 ft. on shore increasing to about 16,000 ft. offshore. The 3 main aquifers in the Coastal Plain are as well as aquifers investigated in a small basin in the White Sand area are described under (a) and (b) respectively of (A) below. Some aquifer properties are given in (B) below:

(A) Description of aquifers

(a) Coastal Plain area: 3 main aquifers have been identified in the Coastal Plain area, viz. the 'Upper' sand, the 'A' sand and the 'B' sand. The 'Upper' sand aquifer outcrops in the White Sand area. Insufficient information is presently available to positively determine whether or not the 'A' and 'B' sand aquifers are recharged.

The ‘Upper’ sand is the shallowest of the 3 aquifers. It occurs at depths varying from 100 to 200ft. in an easterly direction, with thicknesses correspondingly ranging from 50 to 400ft. It is not a much used aquifer because of the high iron content (more than 5 mg/1) and salinity (up to 1200mg/1). Wells drilled between 1831 and 1908 abstracted water from this aquifer.

The ‘A’ sand underlines the ‘Upper’ sand and intermediate sands and clays. It is found at depths ranging from 300 to 1000ft., thicknesses vary between 50 and 200ft. Most of the coastal water supply is obtained from this aquifer which was discovered in 1913 when the Durban Park (Georgetown) well was drilled. Water from this aquifer requires treatment only for the removal of iron. In the Georgetown area, the piezometric level has fallen from 18ft. above ground level in 1913 to about 15ft. below ground level in 1980, and is currently at depths of 80 -90 ft below ground level.

The ‘B’ sand is the deepest of the 3 aquifers and extends eastward from the Demerara River. Its depth varies from 1200 to 2600ft. and its thickness from 50 to 200ft. This aquifer was identified in 1959. The water form this aquifer contains no iron of significance. Its high temperature and a trace of hydrogen sulphide are treated by aeration. The piezometric level in this aquifer has fallen from 38ft. above ground level in 1959 to 60ft. below ground level in 1980, and is currently falling.

(b) White Sand area: Groundwater is abstracted at several locations in the White Sand area of the Coastal Basin. The groundwater resources of a small basin in the Intermediate Savannahs (Alchika River basin – 11.50 sq. mi at stream gauging site) in 1974. The Alchika river (total catchment area – 13.1 sq. mi.) is a tributary of the Ituni River which is a tributary of the Berbice River. A top unconfined aquifer (depth 110 to 160ft., thickness 38 to 62ft.) were located. Groundwater discharge from the top and bottom aquifers were estimated at *16.6 Imgd and 0.92 Imgd.