Surface water surveys and studies form, despite GWS’s name, an important area of competence. Such studies are usually part of major civil engineering projects such as urban water supply and road construction and/or rehabilitation involving surface water availability, estimation of PMP (Probable Maximum Flood) design floods and droughts for dams, bridges, culverts and dikes. Frequency distributions of droughts play an important factor in the dimensioning and design of dams. In addition, GWS has carried out a good number of water availability studies in ungauged basins for irrigation and small dams.