Sustainability Index of Watershed Using Environmental Restoration Approach

. The condition of the Upper Ciliwung Watershed’s Minimum Erosion Hazard value is still far from expected, since the value is still greater than one. The sustainability of watershed functions is influenced by the value of Minimum Erosion Hazard Rate, Farmer's Revenue, and Food Crop Production Results. The purpose of this research is to build calculation method of Sustainability Index of Watershed Function (IKFD) of Upper Ciliwung and to know the condition of Upper Ciliwung Watershed sustainability. The method of this research is mix method that combine quantitative and qualitative data. Data analysis was done by using Analytical Hierarchy Process (AHP). Based on the method used in this study, the authors build the calculation formula IKFD as follows: IKFD = (ITBEM x 72.8%) + (IPPet x 15.3%) + (IPTPa x 11.9%). The final calculation of IKFD Upper Ciliwung is done through the sum of the multiplication of the AHP value of each indicator with the real condition value of each indicator. After the Upper Ciliwung Watershed Index is obtained, then it is categorized into category classes based on the distribution of figures in the index calculation. The Sustainability Index Value of Upper Ciliwung Watershed Function at present is 30.7% and goes into very less level.


Introduction
The condition of the Minimum Erosion Hazard Level of the Upper Ciliwung Watershed shows that the number is still far from the expected one, since the value is still greater than one. Sustainable conditions in the Watershed can be achieved if the Minimum Erosion Hazard (TBEM) velue is ≤ 1 or potential erosion value is less than the maximum tolerable erosion value [18]. Therefore, efforts are needed to obtain the sustainability of the ecosystem function of the Upper Ciliwung Watershed through environmental restoration, especially for erosion control and food and income fulfillment.
The average value of tolerable erosion (average E Tol) in Upper Ciliwung Watershed is 25.7 ton/hectare/year. While maximum tolerable erosion (maximum E Tol) is 27 ton/hectare/year [12]. The condition of erosion value (potential erosion, maximum tolerable erosion, and TBEM), in the Upper Ciliwung Watershed are as follows: 102.40 tons/hectare/year; 27 ton/hectare/year; and 4.14.
The value of Potential Erosion is obtained by the following formula: (1) In addition to the above populations, this study also uses expert respondents for AHP analysis in terms of policy formulation of environmental restoration model for sustainability of Upper Ciliwung Watershed. Expert respondents consist of two groups of stakeholders involved in the restoration of the watershed environment. The number of samples of the AHP method consists of: 1.) Government The number of research samples from this government element amounted to 7 people.

2.) Academics
The sample of academics included in the expert stakeholder in this study came from college lecturers. Sample of academics amounted to 1 lecturer from the School of Environmental Sciences of the Universitas Indonesia.

Data on Food Crop Production
In addition, to obtain the food crop production index, the food crop production data obtained above is converted first into the productivity of agricultural land for food crops. The formula for obtaining agricultural productivity figures for crops can be seen in Formula (3).

TBEM Condition
The Minimum Erosion Hazard (TBEM) level of Upper Ciliwung Watershed for the period of 2013-2016 is greater than 1. In fact, the upstream Ciliwung watershed ecosystem is in sustainable condition if the value of TBEM is ≤ 1 [18]. This shows that the condition of Upper Ciliwung watershed ecosystem can not be said to be sustainable because the potential erosion is greater than the maximum tolerable erosion.

Farmers Income Conditions
The total income of farmer households between the two groups (forest farmers and non-forest farmers) can be seen in Table 1.

Indicator 3.4.1.1 Minimum Erosion Danger Rate (TBEM)
The researcher determines second requirement to be benchmark in this research, which is the value of TBEM ≤ 1.
The Minimum Erosion Danger Rate Index (ITBEM) value is formulated using the following formula: : If TBEM value is less than 1 (one), then it is assumed that the value becomes 1 (one). It is conducted to meet the prevailing rule (concept) (determined by the researcher) in this equation, that the result of comparison has to fall on the used scale, which is 0-100. It is in line with the theory since by assuming the TBEM value which is less than 1 (one) into the value of 1 (one), then it will not change the meaning of the TBEM quality, which remains in a sustainable condition.

Farmer Revenue
Farmer Revenue Index (IPPet) value is formulated as follows:

Crop Production
Crop Production Index (IPTPa) value is formulated as follows:

Sustainable Condition of Upper Ciliwung Watershed
The methods of calculation for IKFD of Ciliwung Hulu are as follows:

Calculation of Minimum Erosion Danger Rate Index (ITBEM) of Upper Ciliwung Watershed (Real (biophysical) condition of Minimum Erosion Danger Rate (TBEM) indicator of Upper Ciliwung Watershed)
According to the calculation based on the data and formula used in this research, TBEM value of Upper Ciliwung Watershed is 4.13. Therefore, according to formula (5) After that, Farmer Revenue Index (IPPet) value of Upper Ciliwung Watershed as in formula (6) is calculated using the following calculation step: (6) = 0.594 or 59.4 %

Calculation of Crop Production Index (IPTPa) of Upper Ciliwung Watershed (Real (biophysical) condition of Crop Production indicator at Upper Ciliwung Watershed)
The value of Crop Production of Upper Ciliwung Watershed based on data processing and analysis methods in this method of research is 25,617.83 tons/year [5,8].
The next step is to obtain the productivity number of agricultural area for crop at research watershed (area) which can be seen in formula (3). After that, the number (value) of Crop Production which can serve as comparison (target) for the number (value) of Crop Production at research watershed (area) is determined. The area is Tasikmalaya City (Citanduy Watershed) [5,8,9,10]. The Crop Production value of Tasikmalaya City (Citanduy Watershed) is 86,191.61 tons/year [10]. The next step is to obtain the productivity number of agricultural area for crop at watershed (area) which can serve as comparison (target) (Tasikmalaya City (Citanduy Watershed)) using formula (3).
The final step is to compare productivity value of agricultural area for crop at research watershed (area) and productivity value of agricultural area for crop at watershed (area) which can serve as comparison (target) of research area, based on formula (7). Ciliwung Hulu. Table 2 shows the result of categorization by the researcher.

Conclusion
The Deforestation and forest degradation are activities that contribute significantly to 17% of global greenhouse gas emissions [15]. Therefore, in addition to supporting the preservation of watersheds, reducing deforestation and forest degradation is very important in mitigating climate change toward low carbon society.