Dynamic model predictive control sources aktivities of phosphorus (P) in the reservoir in the integrated and sustainable: A case study Cirata Reservoir, West Java.

Abstract

Increased of phosphorus loads in the Cirata Reservoir not only come from freshwater aquaculture using cage culture, but also land development (used) around the reservoir such as settlements, paddy field, and agriculture field are also the source of increasing phosphorus loads entering the reservoir. Increased phosphorus loads in Cirata Reservoir, has impacted on declining water quality of reservoir, a more distinct impact is increased excessive water fertility in the reservoir. These conditionsif not well manage; will continue on phosphorus growing impact in reservoir. The condition is happened in Cirata Reservoir, besides the declining of reservoir environmental characteristic also has implications for the economic losses from utilization of reservoir functions, for example decreasing of fish aquaculture productivity using cage culture, increasing the damage of turbine hydroelectric, and decreasing tourism activity around the reservoir. The aim of this study was to analyze the capacity of Cirata Reservoir from phosphorus loads originating from the source activity inside the reservoir and the surrounding area, to analyze the economic value of total utilization Cirata Reservoir, to determine dominant factor affecting phosphorus load control, and to develop controlling model of phosphorus load in the integrated and sustainable. Data analysis methods for controlling the sources aktivities of phosphorus to the reservoir were carried out into several steps: determination of the load capacities of phosphorus in the reservoir with a capacity model; the feasibility business by using instruments of investment criteria (net present value and benefit cost ratio); determining dominant factor of implementation model for controlling phosphorus load through assign the influential sources of phosphorus loads as the dominant factor; control of phosphorus, loads in an integrated and environmentally sound approach that was built with dynamic system model using the Stella 9 software. The results showed that the loads allocation of phosphorus were indicated different amount such as from the area around the reservoir provide about 176.28 mg/m3, fish farming provide about 467.41 mg/m3, and inside the reservoir itself provide about 128 mg/m3. Phosphorus load capacity for intensive aquaculture using cage culture in Cirata Reservoir has a negative value indicating phosphorus load allocation is not accommodated by the reservoir. Dominant factor that plays the role in the implementation model, such as settlement, paddy field, the number of cage culture and phosphorus load by dumping the waste water through the outlet.

Peningkatan jumlah fosfor dalam perairan Waduk Cirata berasal dari aktivitas pemanfaatan lahan di DAS Cirata dan aktivitas budidaya ikan sistem KJA. Pemanfaatan lahan di sekitar waduk berkembang menjadi lahan pemukiman, sawah, dan lahan pertanian. Peningkatan beban fosfor di perairan Waduk Cirata, berdampak terhadap menurunnya kualitas perairan waduk, dampak yang lebih nyata terjadinya peningkatan kesuburan perairan waduk yang berlebihan. Kondisi perairan waduk yang demikian bila tidak diupayakan pengendaliannya maka dampak beban pencemaran fosfor terus semakin meluas. Kualitas perairan waduk yang buruk telah berimplikasi terhadap kerugian ekonomi dari pengusahaan fungsi waduk, diantaranya telah terjadinya penurunan produktivitas budidaya ikan sistem keramba jaring apung, meningkatnya kerusakan turbin sebagai unit peralatan pembangkit listrik tenaga air (PLTA) dan menurunnya minat wisatawan berkunjung ke waduk. Tujuan penelitian menganalisis daya tampung perairan Waduk Cirata dari beban fosfor yang berasal dari sumber aktivitas di dalam waduk dan daerah sekitarnya, menganalisis nilai ekonomi total pemanfaatan Waduk Cirata, menentukan foktor dominan yang mempengaruhi pengendalian beban fosfor dan membuat model pengendalian beban fosfor secara terpadu dan berwawasan lingkungan Waduk Cirata. Metode analisis data pengendalian aktivitas sumber fosfor ke waduk dilakukan: penentuan kapasitas tampung beban fosfor di waduk dengan model daya tampung; kelayakan usaha menggunakan instrumen kriteria investasi (net peresent value dan benefit cost ratio); penentuan faktor domianan pengendalian beban fosfor dilakukan dengan menetapkan sumber beban fosfor berpengaruh dijadikan faktor dominan; pengendalian beban fosfor secara terpadu dan berwawasan lingkungan dibangun dengan pendekatan model dinamik menggunakan program Stella 9. Hasil penelitian menunjukkan daerah sekitar waduk memberikan alokasi beban fosfor ke waduk sebesar 176.28 mg/m3, budidaya ikan memberikan alokasi beban fosfor sebesar 467.41 mg/m3 dan di perairan waduk tersedia fosfor 128 mg/m3. Daya tampung beban fosfor untuk budidaya perikanan secara intensif dengan sistem keramba jaring apung di Waduk Cirata sudah bernilai negatif yang menunjukkan alokasi beban fosfor budidaya sudah tidak tertampung oleh waduk.