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Drought Index For Rarotonga. Rarotonga Water Supply. Impact of drought on Rarotonga water supply. Temporary measures. By-passes upstream of water intakes are formed to harvest available water in the streams. Managing Drought. Water use monitoring Trap more water Roof catchment
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Temporary measures By-passes upstream of water intakes are formed to harvest available water in the streams
Managing Drought • Water use monitoring • Trap more water • Roof catchment • Water Restriction • Water Conservation • Restriction of non essential uses • Monitoring/Predicting Drought
Measuring Drought To manage drought we need to measure it Precipitation based • Standardized Precipitation Index (SPI) • Weighted Sum Precipitation Index
Weighted Sum Index Uses a time window with increasing weight given to most recent rain (a measure of catchment memory)
Drought Forecast Long term rainfall forecast allows a forecast of drought persistence
Experimental Rainfall Prediction Rarotonga: Most recent forecast Rarotonga: September 1996
Useable drought forecasts: • Understanding of the meaning of long-term rainfall forecasts • Understanding of relationship between rainfall & catchment yield • Drought response plan
Conclusion • A drought index provides basis for management decisions • A reliable drought forecast would make it possible to make an earlier decision and the response will be more effective • The simple drought index “Weighted Sum” is a first step in measuring drought, this will be adapted as we gain experience and more data