24 Springs in the Water Cycle: Supply, Water-rock Interaction, and History

Tuesday, 15 March 2005
1:00 PM - 4:00 PM

CAPPED SPRINGS AS A DOMESTIC WATER SOURCE IN SOUTHERN ETHIOPIA

Paper number: 24-2
Program: THEME SESSIONS
Time: 1:20 PM – 1:40 PM

Authors

Abstract

In Southern Ethiopia less than 15% of the rural population have access to potable water. The region has many natural low flow seeps and springs that are being developed with simple gravity feed distribution systems. In this paper, we report on how springs are developed at minimal cost and the results of analyzing the spring water for concentrations of major solutes, nitrate, a septic indicator, and the stable isotopes of water. The eye of low yield springs is isolated and then capped with concrete holding walls with concrete reservoirs. The collected water is then distributed via by metal pipe up to many km from the spring to easily accessible waterpoints, washbasins, and livestock troughs.

Most of the springs discharge from local flow systems at scales of only tens of meters. Concentrations of base cations (Ca, Mg, and Na) are typical of what would be expected from water-rock interaction of volcanic minerals and precipitation water. The d18O and dD values of waters unaffected by shallow evaporation form a local meteoric water line of dD=8.1d18O+19.0. Dissolved nitrogen concentrations occasionally exceed 6 mg/L (as N) and phosphate more than 0.2 mg/L, probably due to animal husbandry upgradient of the springs.