EVALUATION OF AVAILABLE WATER BY METEOROLOGIC IN OPAK WATERSHED (ABSTRACT)

This is abstract of my essay for obtain graduate degree in Departement of Geography and Environmental Science, Faculty of Geography, Gadjah Mada University (1st September 2005 - 4th August 2009)

Supervisor : Emilya Nurjani, S.Si., M.Si.
Examiner : Prof. Dr. H.A. Sudibyakto, M.S.
Guest Lecture : Drs. Retnadi Heru Jatmiko, M.Sc.

Exam : Tuesday, 4th August 2009, 09.00 - 10.15 AM at Meeting Room 3 New Building of Geography Faculty

By : Dwi Ermi Irhami (05/186757/GE/05692)

The aims of the research are : 1) to know the amount of water availability on the rain probability of 60% and 80% based on meteorological water balance, 2) to evaluating available water by meteorological in Opak watershed.

The research uses the primary and secondary data. The primary data include the soil texture data. The secondary data include data of monthly rainfall, the air temperature, transversal position of rain station, and the land use. The samples used in the research are soil samples to determine the soil texture of every set of soil. The sample determination of soil samples is carried out by proportional sampling. Sample of soil taken parallel on its level, that is sub grup. Soil texture every set of land used to count WHC (Water Holding Capacity) value every rain station. The water availability is counted based on the meteorological water balance of Thornthwaite-Mather on the rainfall probability of 60% and 80%. The rainfall probability of 60% and 80% is counted using the frequency analysis.

Based on the result gained, the total of available water on the rainfall probability of 60% in Opak watershed is 433.559.086 m3/year. Available water in upstream is 197.983.623 m3/year, include the high water availability class. Available water in the middle is 197.808.349 m3/year, include the high water availability class. Available water in downstream is 37.767.113 m3/year, include the low water availability class. The average water availability in Opak watershed on the rainfall probability of 60% is 144.529.695 m3/year. The total of available water on the rainfall probability of 80% in Opak watershed is 224.735.368 m3/year. Available water in upstream is 122.635.134 m3/year, include the high water availability class. Available water in the middle is 89.539.643 m3/year, include the high water availability class. Available water in downstream is 12.560.592 m3/year, include the low water availability class. The average water availability in Opak watershed on the rainfall probability of 80% is 74.911.789 m3/year. The water availability in the upstream is high because high rainfall surplus, high place height cause high rainfall. The water availability in the middle is high because the middle area is wide and high rainfall. The water availability in the downstream is low because low rainfall and the downstream area is narrow. The land use influense the level of available water, every type of land use influence high or low of WHC value and potential evapotranspiration that will influence the rain surplus level at the region.

Key words : water balance, surplus, water availability

-Memmy-