Merdada Lake is situated in the area of Dieng plateau which is administratively located in Karang Tengah village, Batur district, Banjarnegara regency, Central Java province. The lake covers around 75 ha of catchment area and 22 ha of inundated area to accommodate 518,520 m³ of water. This lake played an important role as water resource used for agriculture activities around the lake as well as to support the ecology and ecosystem of the area. Even though the catchment area is relatively small, the lake has never run out of water despite its continuous use for irrigation of wide horticulture activities, especially the potato farms.
The lake is mostly used for farm irrigation while partly is still in the forms of forest and bushes. The farm covers 44 ha of land, while the rest 11 ha is still forest and bushes. Because of its significant potential and role of the water resources in the community’s economy, the government should pay attention to the lake.
In 2010, a collaborative program was conducted by the Office of Serayu-Opak River Basin Development (BBWS.SO) and Center of Agro-ecology UGM involving research team from Department of Agricultural Engineering Faculty of Agricultural Technology UGM by building water tower, stoning the terrace, and planting the conservation plants. The water tower was built to reduce the cost of water for irrigation, while the stoning and planting activities aimed to reduce the land erosion and sedimentation as well as to protect the water by optimizing the infiltration and reducing the surface runoff. The program involved the farmers around the lake who acted to be the executors. Prior to the program, dissemination was conducted to get input from the community so that the program meets what they needed.
In this integrated conservation program, the improvement was also applied to the drainage channel and the drop structure. A good quality drainage system was able to reduce the land erosion and optimize the land utility as well as reduce the unused water. The improvement of the drop structure aimed to optimize the drop structure and to reduce the impact of energy resulted by the water current which was potential for causing erosion. According to the plan, the tower functioning as water container was placed in the highest point in the area. The utility of tower instead of water container allowed easier provision and relocation to the ideal spot. The two water towers with capacity of 1500 liter (total 3000 liter) were connected to one pipe lining to the pump and several output pipes for water distribution to the land.
The improvement and strengthening of the terrace were conducted by improving its physical structure and placing stones to strengthen the front part of the terrace. The same rules were applied also in the improvement and strengthening of drainage channel and drop structure. The terrace was planned to be 1 meter tall, but in the execution it was adjusted to the condition due to the various horizontal condition of the interval. The conservation plants were planted in the area of 2-3 ha at the edge part of the farm land with 6 meter interval as planned. The conservation plants were expected to be able to improve the covering ability of permanent vegetations onto the land and the water.
ACKNOWLEDGEMENT: This program could not be realized without financial support from Main Office of Serayu-Opak River Basin Development (BBWS.SO), Yogyakarta. For that reason, our thank is addressed. Our thank is also addressed to our team: Prof. Sahid Susanto (team leader), Ir. Sukirno MS., Prof. Sigit Supadmo Arief, Prof. Moch. Maksum from Faculty of Agricultural Technology UGM and Ir. Adjat Sudrajat MT., from BBWS.SO, Yogyakarta for their contribution in the program.