Drought assessment tools for agricultural water management in Jamaica.

摘要

Increasing urban development, in addition to changing climatic conditions, are just a few of the factors negatively impacting Jamaica's water resources. Therefore, conceptual tools are required for the management of water resources during water scarce conditions. Such tools include drought indices, irrigation requirement guidelines and computer simulation models for irrigation planning.;Two drought indices, the Standardized Precipitation Index (SPI) and the Normalized Difference Vegetation Index (NDVI), were used for the study sites. Both indices were correlated to simulated monthly available soil moisture. It was found that the relationship between each index and soil moisture varies from month to month, with drier months resulting in better correlations than wet months. Predicted available soil moisture values have been calculated for the different SPI categories. It was found that available soil moisture is lowest in the months of March and April. In addition, irrigation requirements were determined for the Moderately Dry and Severely Dry SPI categories of drought in the drier months of the year, for the three study locations, for both vegetables and sugarcane.;SWAT was used to model the hydrology of the Rio Nuevo watershed in St. Mary, Jamaica. SWAT was calibrated and validated using measured streamflow data from the period 2002 to 2007, and achieved satisfactory model performance, with a Nash-Sutcliffe Efficiency of 0.78 for calibration and 0.52 for validation. The SWAT model results were used to determine streamflow capacity for irrigation demands in an agricultural sub-basin of the watershed, and it was found that during the drought year of 2000, there was not enough streamflow to meet irrigation demands of January and March.;Monthly irrigation demands were calculated for three sites in Jamaica: Savanna-la-mar in the parish of Westmoreland, Beckford Kraal in the parish of Clarendon, and Serge Island in the parish of St. Thomas. This was done using simulated monthly available soil moisture values averaged over a 30 year period, for both vegetables and sugarcane. The greatest irrigation demands were found to be in the dry period of January to April, as well as July to August for Savanna-la-mar and Beckford Kraal. Serge Island, however, needs irrigation throughout the year.