ESTIMASI DEBIT MAKSIMUM SUB DAS GAJAHWONG KABUPATEN SLEMAN DAERAH ISTIMEWA YOGYAKARTA

Abstract

; "> This research is aimed to find out 1) The geographical condition in research area
in line with rational method to estimate Gadjah Wong river’s water discharge. 2)
Morphometrical data in research area of Gadjah Wong Sub Watershed. 3) The
volume of Gadjah Wong’s water discharge in the research area for certain period
2 years, 5 years, 10 years, 25 years, 50 years in 100 years. This research is a
descriptive research done by rational method. The data are the characteristic
data found in drainage area and hydrometeorogical data. The average amount of
rain is calculated by polygon thiessen, the precipitation will be analyzed using
Long Pearson Type III statistical method. Meanwhile, the maximum water
discharge will be calculated using rational method of Q = 0,277 CIA. The result
shows that: 1) the geographical condition of research area is located in Sleman
district, Yogyakarta and Bantul district. The geological formation is structured by
solid volcanic rock, while according to Schmidt Ferguson the area is included
into subtropical region. The regosol soil is used as settlement area. The slope
declivity of this area is 0-3%. 2) The morfometric area is 23,27 km2, the river
declivity is LS 0,25, and the sub watershed structure is lengthwise. 3) The amount
of maximum water discharge for 2, 5, 10, 15, 25, 50, 100 years are 30,47 m3/
secs., 73,71 m3/ secs., 111,38 m3/ secs., 164,40 m3/ secs., 205.,0 m3/ secs., and
248,29 m3/ secs.