Copyright © 2018 Runi Asmaranto, Antonius Suryono. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (4) (2018) 4528-4533 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET doi: 20311 Research paper Environmental carrying capacity review in cengklik reservoir Runi Asmaranto 1 *, Antonius Suryono 2 1 Water Resources Engineering Department, Faculty of Engineering Universitas Brawijaya – Indonesia 2 Operating and Maintenance Working Unit of Bengawan Solo River Basin – Indonesia *Corresponding author E-mail: runi_asmaranto@ub.ac.id Abstract Reservoir is a body of water that is formed or modified by humans by damming the river for a particular purpose and can be controlled in its use. Cengklik Reservoir besides its main function as irrigation facilities covering an area of 1,578 ha, is also used for tourism activities and aquaculture. However, on December 29th, 2015 many of the fish in the reservoir died. Cultivated fish died suspected to be caused poisoning by reservoir water that contaminated with waste. This study aims to examine the contamination conditions of the current Cengklik Reservoir and how the reservoir zonation for carrying capacity of the growing floating net cage cultivation. This study was conducted using descriptive analysis method based on the results of qualitative and quantitative tests of primary data in the form of water quality of Cengklik Reservoir. The method of research conducted through 4 stages namely preparation, data collection, data analysis, analysis of results discussion and conclusion. It is expected that the results of this study can be used as a review of Reservoir zonation management and the handling of contaminated reservoir problems. Keywords: Cengklik Reservoir; Reservoir Zonation; Floating Net Cage. 1. Introduction Cengklik Reservoir is located in Ngargorejo Village, Ngemplak Sub district, Boyolali Regency, Central Java Province wherein originally (during the Dutch East Indies Government in 1923) was built to meet the needs of industrial water of Colo Madu Sugar Factory, but starting in 1998 the utilization of its water has been developed for irrigation purposes by increasing the water suppletion from Kali Pepe by constructing the Watuleter Weir along with its suppletion channel, with an effective volume of 9,773 million m 3 and inundation area 10,69 km 2 [1]. In addition to the main functions as irrigation facilities covering an area of 1.578 ha, Cengklik Reservoir is also used for tourism activ- ities and aquaculture. However, on December 29th, 2015, many of the fish in the reservoir died suspected as a result of poisoning by reservoir water that contaminated with waste [2] [3]. According to Maryanto, Head of the Fish Cultivation Group of Floating Net Cage at Ngargorejo Village Ngemplak Boyolali, pollution of the reservoir water is caused by the excessive use of chemical fertilizers from farmers' paddy fields which are then carried by the rainwater to the reservoir. So, it can be suspected that the fish in the reservoir died due to lack of oxygen. The problem of eutrophication is the main cause of decreasing the quality of water, thus disrupting its allot- ment, so that the mass mortality of fish can occur due to decreased water quality as well as less attention to the bearing capacity of the waters. Based on the above problems it is very important to examine the contamination condition of the current Cengklik Reservoir and how the reservoir zonation for carrying capacity of the growing floating net cage cultivation. 2. Literature review Eutrophication is a process of enriching the nutrients in a waters caused by an increase in the nutrients intake that cause eutrophica- tion of N and P which trigger the emergence of ecosystem changes that characterized by an abundance of algae species and aquatic mac- rophytes [4]. Nutrient as the cause of eutrophication in lakes and res- ervoirs can come from 2 sources, namely from watershed and from the waters of the reservoir itself. Pollutants in the form of nutrients entering the reservoir through runoff. Runoff that passes through residential areas and agricultural contain high phosphorus as a result of increased use of agricultural fertilizers that can be the cause of eutrophication in rivers and reservoirs [5]. 3. Material and methods Sumitomo and Nemerow (1970) (in Attachment II, the decree of the Minister of Environment of the Republic of Indonesia No.115 Year 2003 [6]), proposes an index relating to a significant contam- inant compound for an allotment/ allocation. This index is ex- pressed as the Pollution Index (PI) which is used to determine the level of relative pollution to the allowable water quality parameters. This index has a different concept with the Water Quality Index. The Pollution Index is determined for an allotment, then it can be developed for some allotment for all parts of the water body or part of a river. Water quality management on the basis of PI can provide input to decision makers in order to assess the quality of water bodies for an allotment and take measures to improve quality in case of qual- ity deterioration due to the presence of pollutant compounds.