The performance of contour hedgerows for soil and water conservation in the drylands was examined in terms of the ‘water cost’ as transpired by the trees and the ‘amount saved’ as reduction in runoff. Analysis of long-term data obtained from Machakos District, Kenya, showed that the water cost of 4-m contour hedgerows exceeded the amount saved by 3–4 times, indicating that research should focus on wider spaced (12–14-m) hedgerows even though narrow hedgerows are more efficient than grass strips in both soil conservation and overall water utilisation. Future research should also include trees which can enhance soil fertility as well as soil conservation, use economically useful tree species, and examine the constraints to farmers' adoption of such technologies.