Penentuan Nilai Modulus Drainase pada Sawah Beririgasi di Daerah Irigasi Namu Sira-Sira Kecamatan Sei Binge Kabupaten Langkat

Abstract

This Research aim to know drainage modulus value (Dm) that is amount of excess of water which must be thrown perday at Namusira - sira Irrigation Area in Langkat Regency, so that can be designed drainage channel dimension matching with rice growth so that rice growth become optimumly. To know Dm value used 2 method that is method plot daily maximum rainfall and use formula of Public Work Department. From result of research, obtained Dm value at daily method plot maximum rainfall is 16 mm / day or 1,85 lt/det/ha. By using formula of Public Work Department is 26,96 mm/ day or 3,12 ltldetlha. So that require to be designed an appropriate drainage channel to accomodate and conduct excess of water exist in Namusira - Sira Irrigation Area. The level of difference of Dm value for both of the method is because of there is difference of high flooding water minimum.At plot method maximum rainfall, the high flooding to used is 150 mm, forwhile at using formula is 50 mm. Beside that, at plot method maximum rainfall percolation and potential evapotranspiration do not be reckoned, forwhile using formula method of Public Work Department used value of percolation and potential evapotranspiration ( ETo) from Namusira - Sira Irrigation Area.