A spatial aggregation index for effective fallow decision in paddy irrigation demand planning

As irrigation demands usually take the largest share of water supply, paddy fallow is considered as a drought relieving measure in some Asian paddy growing countries by transferring the water saved to the municipal and industrial sectors. But the relationship between fallow area and irrigation demand reduction is not necessarily linear, there may be more than dozens combinations of fallow farm that can meet the same amount of irrigation demand reduction requirement. The Joint Count Statistics (JCS), an index commonly used in spatial analysis to measure the spatial coherence among cells was modified as a spatial aggregation index for evaluating the irrigation demand reduction effectiveness from a spatial perspective. This Modified JCS is supposed to identify the degree of spatial aggregation by taking underlying irrigation network into considerations. The modified JCS was proved to be effective to identify better fallow pattern through a case study in Taiwan.