Some Physical and Chemical Properties of Water from an Undisturbed Tropical Catchment Area (Guma Dam,Sierra Leone)

The water had a very low content of total suspended solids (<1 mg l^?1), but its transparency was high (5–8 Hazen units). The concentration of Mg⁺⁺ and Ca⁺⁺ were below 1 mg l^?1, but that of SiO₂ was 5.3 mg l^?1. Free CO₂ was abundant (15.3 mg l^?1) and the pH was low (<6.5). These conditions were accompanied by low concentrations of PO₄-P, total iron and NO₃-N. The DO content of the water was always below 80 %, but the chloride concentration (8.4 mg l^?1) seems relatively high for this type of freshwaters. It is, however, much lower than that known for arid areas. It is concluded that the geology and vegetation dominate the chemistry of the water from the Guma Dam catchment area. The influence of man is acknowledged only in as far as he has protected the catchment area.