From this page, you can estimate the spending needs associated with developing all the economically viable irrigation potential in your country of choice, based on parameters of your own choosing.
The irrigation spending needs model is based on spatial analysis of the economic viability of irrigation investments. For each half degree (10x10 kilometer) pixel of land, the model determines the cost of developing irrigation infrastructure, and the projected improvement in net revenues resulting either from increased yields of existing crops or switching to higher value crops. If the balance of costs and benefits is favorable, the pixel is considered suitable for irrigation development.
Data for this model is drawn from three spatial data sets namely current crop distribution, spatially-explicit crop specific biophysical potential, and potential runoff and effective rainfall from a hydrological model for small-scale irrigation. Crop prices, based on commodity-specific world prices for 2004–06, were adjusted for country differences in price policy and market transaction costs. The model is based on a 50-year horizon: notionally 2006 to 2056, and the discount rate is 12 percent.
The model considers two different types of irrigation.
Large scale irrigation: For land located downstream from existing or planned hydro-power projects, the possibility of developing large scale irrigation schemes is considered in any areas that meets basic criteria for agro-ecological suitability. It is assumed that the costs of water storage are entirely covered by hydro-power, and that only water distribution costs need be considered for irrigation. The baseline cost assumption is US$3,000 per hectare.
Small-scale irrigation: For all other land, the possibility of developing small scale irrigation is considered, based on small reservoirs, farm ponds, treadle pumps and water harvesting structures collecting local runoff. Attention is limited to areas that have adequate road access to local markets. The baseline cost assumption is US$2,000 per hectare, with a five year reinvestment cycle.