Common Pool Resources
Our hypothesis: the tenure system on any part of the catchment affects the quality of the catchment hydrology. The approach recognises the tenurial and ecological basis of human settlement and land use practices; and couples tenure regimes with landscape ecological analyses. Using GIS, hydrological sub-zones are linked to the ecological and demographic factors, and the extent of degradation.
The impacts of spatial heterogeneity, influenced by the tenure regimes, are explained in terms of hydrological parameters – surface run-off, ground water resources, sedimentation – using multiple regression models. Based on principal component analysis, areas are classified by the extent of degradation and those needing priority attention are identified.
The Save River Catchment Area covers almost 82050 km2 of the total land area of Zimbabwe. It is made up of two major river systems – the Save and Runde rivers – and is typical of a spatial landscape in which socio-economic and environmental activities are degrading the condition of the catchment.
Forty hydrological zones form the basic sampling units for the whole catchment area. The zones are spatially integrated with the tenure regimes.
Use of GIS will give statistics on the geology, land-use pattern, vegetation, topography and human and livestock population densities for each tenure category by area. Then these will be used to couple the land use model to the hydrological sub-model, thereby linking land use, ecology and the observed hydrology of the catchment.
The response variables are hydrological parameters and the percentage of degraded land. For example, run-off is positively related to rainfall (see graphs), and a correlation is assumed between the residual variation – both spatial and temporal – and the tenure regime, land-use patches and ecological mosaics through-out the catchment.
For each tenure category, the following relations will be examined:
1) land use percentage (area) and observed hydrological parameters;
2) the effect of vegetation and soil type on hydrology;
3) the effect of population densities (human and livestock) and poverty status on hydrology and degradation.
The outcome is a spatial quantification of tenure impacts at the catchment level. The relationships can further be modelled to predict the impact of future land use transfers and to come up with “what if” situations. Such scenarios can be used to support research and policies that promote sustainability.