While water control is often not the only limiting factor in crop production in SSA, it is often the starting point for any improvement in agricultural productivity. In many areas, farmers work with poor soils, they have limited financial credit, they apply too little fertilizer, and they are unable to harvest and deliver their crops to market in a timely fashion. However, in many arid and semi-arid regions, the lack of access to water (or inadequate control or timing of water supplies) contributes to the difficulty of generating acceptable yields. In addition, uncertainty regarding rainfall or access to a developed irrigation supply causes farmers to apply less seed and fertilizer than they might otherwise do. Hence, efforts to improve farm-level access to water and control of water deliveries or rainfall will, in the zones identified in the Chapter 3, enable farmers to improve productivity within current cropping patterns and to consider diversifying their crop choices, thus progressively increasing the proportion of their marketable surplus, albeit locally.