Daerah Irigasi Pemali Hilir yang berada di Kabupaten Brebes memiliki luas area irigasi sebesar 25.180 Ha dan mendapat pasokan air Sungai Pemali dari Bendung Notog yang terletak di Kecamatan Songgom Kabupaten Brebes. Namun, seiring berjalannya waktu banyak permasalahan yang muncul diantaranya bertambahnya kebutuhan pemakaian air irigasi, terjadinya perubahan iklim, pola tanam tidak teratur, dan penyempitan saluran irigasi akibat sedimen yang mengakibatkan suplai debit air untuk irigasi tidak maksimal. Untuk mengatasi permasalahan di atas, diperlukan upaya analisa keseimbangan air irigasi. Dalam studi ini, analisa keseimbangan air irigasi dilakukan dengan mencari besarnya ketersediaan air irigasi dan kebutuhan air tanaman. Hasil dari studi ini ialah jadwal pola tanam dan perbandinganantaraketersediaan air irigasidankebutuhan air irigasi.Dari hasilperhitungan ketersediaan air irigasi, diperoleh 3 alternatif pola tanam diantaranya bawang – padi – bawang, bawang – padi – kedelai, dan bawang – padi – kedelai dengan masa penyiapan lahan awal bulan Agustus, September, dan Oktober dan awal tanam bulan Nopember. Berdasarkan pola tanam terpilih, bahwa kebutuhan air irigasi untuk masing masing alternative pola tanam 1, pola tanam 2, dan pola tanam 3 terpenuhi dan seimbang.

Pemali Hilir Irrigation Area located in Brebes Regency has an area of 25,180 Ha irrigation and River water supply gets Pemali from Weirs Notog located in Songgom Subdistrict Brebes Regency. However, over time many of the problems that arise include the increasing use of water for irrigation needs, the occurrence of climate change, the cropping pattern is irregular, and the irrigation channel constriction due to sediment supply resulting in discharge water for irrigation is not maximal. To address the above problems, it takes are effort of irrigation water balance analysis. In this study, an analysis of water balance of the irrigation is done by searching for the value of the availability of irrigation water and water needs of plants. The result of this study is the cropping pattern layout and schedule of comparison between the availability of irrigation water and water needs of plants. From the calculation of the availability of irrigation water, three alternative cropping patterns are onion - rice - onion, onion - rice - soybean and onion - rice - soybean with land preparation period beginning August, September, and October and early November planting. Based on the selected cropping pattern, the irrigation water needs for each alternative cropping pattern 1, planting pattern 2, and cropping pattern 3 are fulfilled and balanced.