Analisis ekonomi alokasi optimal sumberdaya air antar wilayah dan pengguna di pulau lombok: aplikasi model optimasi dinamik

Abstract

Water scarcity has been an increasing concern among countries. It is estimated that the World would face critical water scarcity by the year of 2025. Water Demand of Lombok has tremendously increased by 10 times during the last decade, while its supply tend to gradually deteriorate overtime, lead to an intense competition and conflict among users. This research was aimed to address the issues of efficient and fair water allocation among competing production sectors and regions, and specifically to: (1) estimate water demand and supply functions, (2) develop an existing optimal water allocation model, (3) simulate the effect of food self sufficiency and aggregate pumping quota policies under different discount rate and economic growth scenarios on the water allocation, groundwater remaining stock and the value of net social benefit, and (4) determine the economic value of water among sectors. The objective of the optimization model was to maximize the net present value of social benefits generated by all production sectors and consumers (households) under some hydrologic and socio-economic constraints. Dynamic Non Linear Programming was employed to determine the optimum level of water allocation, and General Algebraic Modeling System (GAMS) was used to solve the problems. The Results indicate that bottled water demand is considered the most price elastic among other water demands, while all of virtual water demands, except for tofu, are also considered price elastic. Water allocation/consumption varies among policy, discount rate and economic growth scenarios, and tends to gradually decrease overtime for all sectors. The value of social benefit also differs among policy scenarios, reaches up to Rp.10.81 trillion for 16 years time horizon. Agriculture consumes the highest level of surface water, reaches up to 54%, while tourism sector consumes about 18 %, and the rest was consumed by domestic user and industry. Tourism sector consumes the highest level of groundwater (72%). Under food self sufficiency policy, groundwater remaining stock is the least among other policy scenarios, and will be exhausted by the year of 2017, while aggregate pumping quota could maintain sustainable groundwater stock overtime. Marginal user cost of water under Food Self Sufficiency Policy is the greatest among others.

Penurunan ketersediaan dan supply sumberdaya air dewasa ini menjadi issue lingkungan paling penting yang dihadapi oleh berbagai negara. Diperkirakan hampir dua per tiga dari seluruh bangsa di dunia ini akan mengalami kesulitan sumberdaya air pada tahun 2025 (United Nations Environment Programme, 2002). Cepatnya pertumbuhan penduduk disertai dengan peningkatan standard hidup, urbanisasi, dan pertumbuhan industri, telah menyebabkan peningkatan permintaan, kompetisi dalam penggunaan, dan konflik antar sektor pengguna air. Kebutuhan air Wilayah Nusa Tenggara Barat mengalami peningkatan signifikan (10 kali) pada periode 1990-2000 , dan diprediksi pada tahun 2015 meningkat 45%, dan 12% pada tahun 2020. (ESCAP, 2000). Kebutuhan air mencapai 4.164 milyar mP3 Pper tahun yang terdiri dari 2.319 milyar mP3P (55.68%) untuk sektor pertanian, 832.92 juta mP3P (20%) untuk sektor industri, 179.95 juta m3(4.32%) untuk sektor domestik, dan 832.81 juta mP3P (20%) untuk kebutuhan lainnya (Balai Hidrologi Propinsi NTB, 2004). Sementara permintaan sumberdaya air di satu sisi cenderung terus meningkat, ketersediaannya justru mengalami penurunan. Potensi air permukaan Pulau Lombok sebesar 2.912 milyar mP3P, sedang potensi air tanah mencapai 1.029 milyar mP3P per tahun, jumlah tersebut masih lebih kecil dibandingkan kebutuhannya, sehingga Neraca Air Pulau Lombok minus 223.03 juta mP3P per tahun.