TINGKAT SEDIMENTASI DI MUARA SUNGAI WEDUNG KECAMATAN WEDUNG, DEMAK

Abstract

Muara sebagai penghubung antara sungai dengan laut tidak luput dari terjadinya sedimentasi karena sedimen dari hilir dan laut akan bertemu di daerah muara. Sedimentasi menjadi masalah penting bagi kehidupan manusia maupun organisme yang hidup di dalam perairan. Hal ini juga terjadi di kawasan perairan muara Sungai Wedung, Demak. Kegiatan masyarakat sekitar yang menjadikan sungai mengalami sedimentasi harus lebih disadari agar perairan sungai lebih terjaga kelestariannya. Tujuan penelitian ini adalah untuk mengetahui pola sebaran material organik dan inorganik serta nilai laju sedimentasi dan muatan padatan tersuspensi di muara Sungai Wedung. Penelitian dilaksanakan pada bulan September-Oktober 2013 di perairan muara Sungai Wedung Kecamatan Wedung, Demak dan analisa laboratorium dilakukan pada bulan November 2013. Materi yang digunakan dalam penelitian ini adalah sedimen yang berada di dalam sediment trap dan air pada masing-masing lokasi penelitian. Metode pengambilan sampel yang dipakai adalah purposive sampling. Analisis data meliputi laju sedimentasi, tekstur sedimen, muatan padatan tersuspensi dan bahan organik total. Lokasi penelitian dibagi menjadi 4 titik yaitu titik 1 dan 2 di muara dekat daratan, titik 3 tepat di laut dekat muara dan titik 4 berada di laut dekat delta. Hasil penelitian menunjukkan bahwa sebaran material inorganik pasir (sand) lebih tinggi di kawasan laut, sebaliknya lumpur (silt) dan lempung (clay) serta bahan organik lebih tinggi di kawasan muara. Laju sedimentasi di perairan sekitar muara Sungai Wedung berkisar antara 60,839 gr/m²/minggu pada lokasi muara dan 373,242 gr/m²/minggu pada lokasi laut. Nilai TSS di perairan ini berkisar antara 1,277 mg/l pada lokasi muara dan 7,784 mg/l pada lokasi laut. Perubahan TSS berakibat meningkatkan nilai laju sedimentasi dengan peningkatan sebesar 0,0183 gr/m²/minggu setiap 1 mg/l TSS mengikuti model y = 0,0183 x + 147,88 (y = laju sedimentasi dan x = TSS).

Estuary as a link between river and sea is not apart from sedimentation process because sediment derived from downstream and sea will meet in this place. Sedimentation will become important problem for human beings and organism live in estuaries. These also occured in the Wedung Estuary, Demak. Activities from the community live around Wedung River which cause of sedimentation should be stopped in order to preserve river in the future. This research aimed to know spreading pattern of organic materials and inorganic matter,  to estimate sedimentation rate and total suspended solid in Wedung Estuary. This research was carried out in 2 months, started from September-October 2013 in estuary of Wedung Subdistrict Wedung, Demak and laboratory analysis was conducted in November 2013. Materials used in this research was sediment deposited in sediment trap and sample of water taken from each location sampling. Sampling method used in this study was a purposive sampling. Data analysis comprised of sedimentation rate, sediment texture, total suspended solid, and total organic matter. Location of research was divided into 4 location i.e: point 1 and 2 located in the estuary near land, point 3 precisely in the sea near estuary and point 4 located in the sea near delta. The results showed that distribution of sand as organic material is higher in the sea. On the contrary; silt, clay and organic matter content were higher in the estuary. Sedimentation rates in the waters around Wedung River ranges between 60,839 gr/m²/week at estuary and 373,242 gr/m²/week at sea. TSS content ranges between 1,277 mg/l at estuary and 7,784 mg/l at sea. Changes in TSS cause an increase in sedimentation rate 0,0183 gr/m²/week for every 1 mg/l TSS increase following regression y = 0,0183 x + 147,88 (y = sedimentation rate and x = TSS).