Land tenure, and its influence upon streamflow regimes in Zimbabwe

There is limited information concerning the effects of traditional land use upon hydrologic regimes in southern Africa, or in the dry tropics. Significant information is presented regarding the legacy of inequitable land distribution and inappropriate colonial and settler land use policies upon hydrologic regimes and water availability in Zimbabwe.The influence of land tenure and land use upon regional variation in streamflow annual yields, flood magnitudes and storm flow volumes, base flow volumes and low flow characteristics is examined utilising a data base of 110 gauged dambo catchments in central Zimbabwe. At a catchment scale the streamflow regimes of nine basins of contrasting land use and land tenure, representative of various precipitation regimes and basin soil complexes in Zimbabwe are examined using standard probability distributions. Particular attention is paid to determining the effect of land tenure upon streamflow volumes and variability, flood frequency using both the annual maximum and partial duration series, dry season flow characteristics, and streamflow drought regimes using both fixed and practical threshold levels.Regionally, land tenure is an indiscriminate factor in describing catchment hydrologic response. There is some evidence to suggest that communal basins exhibit lower evapotranspiration losses than commercial estates. In association with shallow less permeable dambo soil complexes communal basins tend to enhance dry season flows. At a basin scale clear differences are presented between basins within similar soil complexes in all aspects of hydrologic regime, and are explained in terms of basin physiographic and land use characteristics. Land tenure at a basin scale appears to dominate hydrologic response through differing basin evapotranspiration rates and water management characteristics.As Zimbabwe is undergoing widespread land use change through agricultural resettlement, the results have important implications for the understanding of basin hydrologic response and basin water management.