| Summary: | The availability of water in the Gajahwong watershed in 2012 deficit in some areas
of the service due to droughts that cause discharge decreased up to 40%. In addition,
Gajahwong watershed is one of the nine rivers in the province of Yogyakarta who have
experienced loss of quality, because it is contaminated by sewage. Some pollutant
parameters that have exceeded the quality standard in the Gajahwong watershed namely :
BOD, COD, TSS, phosphates, faecal coliform, and total coliform. The study is expected to
note the relationship of the river to the discharge of water pollution parameters. It can be
studied water pollution control efforts are suitable with the hydrologic characteristics and
capacity of the pollution load in an attempt to realize the benefits of sustainable water
resources .
In the analysis of the water quantity by using a Mock model will obtain availability
of water in form the reliable discharge with graphical Flow Duration Curve method. The
length of rainfall data and climatological data were used for 12 years, starting from 2001
until 2012. Determination of the status of river water quality was analyzed with Pollution
Index Method to determine water quality conditions, whether contaminated or not. Study
the relationship of quantity and quality of water can be described by the relationship
between discharge and water quality parameters that can be known the relationship between
changes in levels of pollution parameters with the water discharge in the Gajahwong
watershed.
Gajahwong watershed reliable discharge 80% outcome of flow duration curve at
monitoring points in Wonokromo was 0,797 m
3
/s. Water quality conditions in the
Gajahwong watershed from upstream to downstream has declined with the status of
moderately polluted. During 2007 to 2012 the levels of TDS, TSS, DO, COD, detergents,
oils and fats, and faecal Coliform has decreased. Concentration of water quality parameters
was increased like BOD, phosphate, and total coliform are causing polluted water.
Gajahwong watershed polluted by TSS, BOD, COD, Phosphates, Detergents, Oils and Fats,
faecal coliform, and total coliform concentration exceeds the threshold for water quality
standards class II according to Governor Regulation Yogyakarta Provincial No.20 of 2008.
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