Agricultural water management interventions such as small reservoirs and dugouts are precious assets in semi arid and arid regions of the world. The Upper East Region of Ghana by virtue of its climatic condition is classified as a semi arid region. It has a total of about 239 small reservoirs on record apart from those unrecorded. They are either or not located on streams and rivers upstream of the Ghana portion of the Volta River Basin, with only about fifteen percent (15%) of these reservoirs not in good condition. There have been significant reductions in the flow of water from all the three main tributaries of the Volta River. The impacts could as well be very significant further downstream where the Akosombo Hydro- power dam (the main source of the country?s electricity supply) gets its source of flow. The effect of many Agricultural water management interventions such as small reservoirs in the Upper East Region of Ghana was investigated using the WEAP model. A total of 239 small reservoirs were identified between the periods 1920 to 2010 and were used in the model. The growth rate of the reservoirs in the various catchments was computed and used in generating the business as usual scenario whiles the increase in number of small reservoirs in each catchment of the Basin was generated using some key assumptions. The model was first adapted to the region and calibrated using measured discharge values. Three different scenarios were incorporated to access the impact of the small reservoirs on the White Volta River. The results obtained indicate that though some of the reservoirs are already experiencing unmet demands, they have some level of impact on the flow of the immediate sub- basins and the White Volta River as a whole. However the creation of more reservoirs as seen in the scenario with increase in the number of reservoirs could have very significant effect from the year 2031 onwards on the flow of the White Volta River and reduce its contribution to the Akosombo Lake which is further downstream in the Volta Basin. Tono and Vea irrigation schemes will record the highest unmet water demand of about 0.00045 Mm3 in the Nawuni catchment between 2038 and 2039. Reduction in stream flow will be significant between 2017 and 2028.