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A comprehensive study of long-term changes in October rainfall patterns in southern Israel, a semi-arid fringe zone between the Mediterranean coastal plain and the Negev Desert, was carried out. It was earlier postulated that the observed positive trend in October rainfall amounts may result from land-use changes in the area following the installation of the National Water Carrier (NWC) in the early 1960s. The purpose of the present study is to delineate the anticipated local effects, as well as their spatial extent, in order to investigate the possibility of climatic change over a larger synoptic scale.

In the study region, a total number of 51 rainfall stations with long-term records up to 55 years, were analyzed, along with six control stations in other parts of the country. All stations were analyzed for trends in early seasonal rainfall, spatial variability during the two reference periods before and after the 60s, and for the ratio between rain per day (RPD) and number of rain days (NRD) during the two periods. The results of the analyses point to a well defined localized climatic change in October rainfall patterns within the study area, that is traceable to intensive and extensive land-use changes following the installation of the NWC.