Raw water for drinking water management model based on watershed

Abstract

Growth of population at Babon watershed area has influenced the demand of raw water significantly and it also causes burden to land use. Population growth consequently will rise the demand for housing, for this reason paddy cultivation and forest area were converted to be a housing area. The effect of housing development will escalate the degree of coefficient run off (CRO). Accordingly, infiltrations of rain fall decreases and it affects the lessening of soil water contain. Besides, population growth and housing development contribute significantly to the decease of water quality surrounding Babon watershed area. Study published by Ministry of Public Work described that in the last 10 years, the damage of watershed is critical and it significantly increase drastically. Data shows that in year of 1995, 20% of watersheds which located in Java island are in critical condition. Extensively in year 2005, the number of critical watershed increase to be 60%. To overcome this situation, conservation of watershed is extremely required, otherwise, in the future population in jawa island will face the lack of raw water. The Raw Water for Drinking Water Management Model Based on Watershed is created in order to overcome the impact of critical watershed condition which influence lack of water quantity and to increase the quality of water. The Model consists of three sub model such as: sub model of raw water supply, sub model of raw water demand and sub model of water quality which has been validated based on structural validation and performance validation. Hence, this model will relevant to apply at other watersheds. By designing a “Raw Water for Drinking water Management Model Based on Watershed”, it is identified that conservation will increase the index of Coeffisient Run off (CRO). If CRO increase, it will influence water infiltration. Hence, supply of raw water as base flow will increase accordingly. The increasing of base flow, will reduce debit of surface water. Along with inceasing of debit, conservation will also increase the index of water quality. hence raw water supplied by watershed will be in category of raw water for drinking water which is called ABAM. If water quality getting better, it will minimize the cost of drinking water production. As a result, the profit of PDAM will increase significantly and it will contribute to fund conservation. In order to ensure that this model can be implemented by stake holders, It also completed by institutional mechanism. By designing institutional mechanism, consequently all stakeholders which are responsible for watershed conservation will work simultaneously.

Bertambahnya jumlah penduduk setiap tahun menjadi penyebab utama meningkatnya permintaan akan sumberdaya air, dilain pihak yang terjadi justru sebaliknya, yakni air menjadi sumber daya yang keberadaannya semakin tak berketentuan, dimana setiap tahun ketersediaannya semakin menurun. Penurunan ketersediaan air bertolak belakang dengan fenomena peningkatan kebutuhan air. Perubahan fungsi lahan atau konversi lahan telah mengakibatkan terjadinya penurunan debit minimum dan peningkatan debit maksimum. Sementara itu, akibat deforestasi dan kerusakan lahan, kemampuan lahan untuk menahan dan menyimpan air makin rendah. Deforestasi dan kerusakan lahan telah meningkatkan koefisien limpasan atau coefficient run off atau CRO, (perbandingan antara volume limpasan dan volume curah hujan), dan menurunkan kemampuan tanah menahan air hujan. Untuk mengatasi masalah tersebut perlu dilakukan pengelolaan air baku yang berbasis DAS. Pengelolaan air baku yang berbasis DAS didasari karena DAS ditentukan oleh hidrologi alami, dimana mewakili basis paling logis untuk mengelola sumber daya air. Disamping itu, DAS merupakan suatu mega sistem yang terdiri dari sub system sub sistem, sehingga penyelesaian dengan pendekatan DAS akan menyentuh permasalahan mendasar yang harus ditangani. Sumber daya air menjadi titik fokus karena permasalahan sumberdaya air adalah permasalahan yang tidak bisa dilepaskan dari masalah lingkungan, ekonomi dan sosial.