Drought analysis in relation to crop production Anuradhapura district

Abstract

In order to identify the risk on drought for crop production in Anuradhapura district. daily rainfall dataover 35 years in seven rain gauge stations were analyzed. The selected stations were Anuradhapura,Mahailluppallama, Nochchiyagarna, Kalawewa, Elayapaththuwa, Padaviya and Vavuniya.

Among all the stations, both highest mean annual rainfall of 1488.5 mm and annual dependable rainfallof 1276.6 mrn were recorded in Padaviya. The minimum rainfall values of I 087.6 mm and 903.1 mrnwere noted in Nochchiyagama respectively. 31% and 69% of total annual rainfall was received inyala and maha seasons respectively. Number of dry weeks in the district was assessed by Hargreaves'Moisture Availability Index (MAl) method and 10 mm and 20 mrn weekly rainfall at 75% probabilitylevel for upland and wetland crops respectively.

Accord ing to MAl, average number of dry weeks in the district was 25 (out of 26) for yala seasonand 19 (out of26) for maha season. The maximum dry period of I 00% was recorded in Nochchiyagama,Elyapaththuwa and Padaviya in yo/a season. It was 85% for maha season in Nochchiyagama andElayapaththuwa. The highest dry run of 42 weeks was recorded in Nochchiyagama, Elayapaththuwaand Padaviya throughout the year. Based on the monthly dependable rainfall 74.5% of total rainfall isconcentrated into last 3 months in the region.

Based on 20 mrn weekly rainfall at 75% probability, the whole district was completely dry during yalaseason. Total 100% dryness was observed in Elayapathtuwa based on 10 mm and 20 mrn weeklyrainfall at 75% probability for maha season. Average 96% of dryness was recorded in the districtunder 10 rnrn weekly rainfall at 75% probability in yala season.

The analysis depicts the risk on drought in the area for crop production. It indicates the irrigation needfor the crop production in the district both in yala and maha seasons.