Determining potential rainwater harvesting sites using a continuous runoff potential accounting procedure and GIS techniques in central Italy

The “Eight Communities of the Chianti” area, Tuscany, Italy, receives an average annual rainfall of 700–800mm, mainly between September and December. Nevertheless, the storage capacity of the soil is not sufficient to fulfill agricultural requirements, resulting in a shortage of water from May to September almost every year. Runoff harvesting structures like farm ponds can be used to augment water supplies in agricultural areas. The suitability of a site for a farm pond requires a careful assessment of spatially varying parameters like runoff potential, slope, and land-cover. Therefore, a spatial analysis and a continuous runoff potential accounting procedure, based on the Soil Conservation Service Curve Number (SCS-CN), was used to evaluate the potential water harvesting. Model evaluation was performed based on daily runoff events recorded at 11 stations between 1996 and 2010. The statistical indices for the evaluation of the model calibration and validation were, respectively, mean percent error, −2.2% and 1.1%; mean absolute percent error, 25.2% and 23.8%; and Nash–Sutcliffe coefficient, 0.80 and 0.81. The analysis indicated that the model was able to estimate the observed runoff reasonably well. The sites suggested by the model were investigated for suitability in the field, and showed an 83% accuracy of the model. Given the increasing demand for water requirements in agriculture, this methodology could be effective in other agricultural areas with similar requirements to the “Eight Communities of the Chianti” area.