Developed watershed classification index determining management priority level based on watershed carrying capacity

Watershed classification index is important in terms of determining watershed management priority level based on its carrying capacity score whereby currently watershed is classified into two indexes which are “to be maintained” if the carrying capacity score is below 100 and “to be restored” if it is above 100. This index fails to capture existing condition where there are watersheds with carrying capacity score in between 90 and 110. The purpose of this paper is to propose developed watershed classification index to determine management priority level based on watershed carrying capacity score. The method used to develop the watershed classification index is Classification Interval approach. The analysis is resulting in rigorous management priority level based on developed watershed classification index which is 50 < carrying capacity ≤ 90 as Priority 3 (watershed indexed as “to be maintained”), 90 < carrying capacity ≤ 110 as Priority 2 (watershed indexed as “to be improved”) and 110 < carrying capacity ≤ 150 as Priority 1 (watershed indexed as “to be restored”). Therefore, the correct management priority level for Gangsa Watershed that has carrying capacity of 106 is Priority 2.


Introduction
Watershed management is a human action aimed to make sure that the usage of the Watershed resources is through the integrated ecosystem approach to maintain those resources by doing a balance conservation of water quantity, land, vegetation, and other natural resources [1], thus decreasing or avoiding the negative impact at the downstream [2]. Considering the fact that Watershed management action needs big fund [3] and involves multi stakeholders, hence urgency level is needed [4]. Watershed management urgency level (Priority Scale) is an important element in watershed management, so that the activity plan that is chosen scientifically can be made right on target in order to be effective, suitable, and sustainable. To determine the category of a Watershed condition wheter it is healthy or not, is by doing the support capability assesment [5]. A healthy Watershed is the one which has ability to supply the needs of all ecosystem [6] that is used as an assesment of how good resources management activity balancing the anthropogenic need, ecology function and integrity in watershed [7]. To determine the watershed health condition, it is necessary to be evaluating and monitoring. Watershed management is important because it can monitor whether the activity is done from time to time and has been progressing to or away from the target [7].
Furthermore, that activity is to asses whether there are changes in the watershed compared to the previous condition, whether those changes meet the set target and standard, and also whether it can be called successful, it needs to be reported to help the sustainable implementation decission guide [8].
The watershed priority scale determination becomes important in terms of watershed management [9] and it is used as management program plan, necessary in developing management identification, developing maintenance plan, and can help taking prevention acts needed in an a priori condition [10], including problems of limited funding [11]. Given the fact that in Watershed management, big investation fund is needed [12], thus a scientific analysis is needed [3]. The current condition in Indonesia is when the watershed classification index based on the support capability is released, where the total score of watershed classification index (<100), watershed support capability is maintained, if (>100), watershed support capability is recovered, thus those results are hoped to project the urgency level of watershed management reviewed [13,14,15], this thing is the problem, where the classification does not scientifically match the class interval score of watershed support capability and its category, hence, need a further review. The purpose of this paper is to determine the watershed classification index as a development to get an image of the watershed management urgency level (priority scale) according to its support capability score.

Fig. 1. Map of Gangsa watershed
Gangsa watershed is one of watershed development (SWP DAS) in Pemali-Comal, where it was ranked on the 9th and 10th out of 11 Prioritized Watershed areas that needed to be thoroughly handled intergratedly in immediate time.
Geological condition of Gangsa watershed is divided into 2: Alluvium and Alluvium Facies. The Alluvium spans 13.442,17 ha across the Brebes District, whereas the Alluvium Facies spans for 6.498,60 ha. The Alluvium plain has a flat topography, which was formed through the process of alluvium deposition at the right and left side of the river.
The monitoring and evaluation impelementation of watershed development have a major necessity and play a big factor in water system protection, supporting the continuity in improving agriculture produtivity, and also as the vital security and protection for residences. At the midle of Gangsa watershed until the downstream, there are urban cities with high citizen density whose existence depends on the upper region: water supply compliance, flood control, environment preservation, and human wisdom in exploiting the available natural resources.

Substance and material
This research uses various supporting tools such as Global Positioning System (GPS) to determine and pinpoint the observation location, ArcGIS application to process the spatial data, digital camera to record the field data, and computer to process and analyze data, also as a research instrument as primary data base.
Substances used in the research consist of Landsat imaging and digital spatial maps such as: Land Coverage map and Land Exploitation map. The map for watershed, river, earth structure, topography, administration, land capabilities, hydrology data covers rainfall volume and sedimentation.

Analytical technique
The analytical technique for processing data is done through several stages. ▪ First stage is to collect and select data, to choose tabulation data, primary or seconday data used within this research. ▪ Second stage is deducing the class classification according to its support capabilities through class interval approach analyzed with MS Excel program. ▪ With two stages done, the process moves on to determine the class classification for watershed support capability scale and its priority scale. ▪ Next is applying the watershed capability scale and prioritizing scale on Gangsa watershed. The watershed support capability assessment is analyzed with the assistance of Excel program, covering 5 (five) criteria which are: land condition, water system, socioeconomic, building investment, and space utilization. ▪ After Gangsa watershed support capability value is gained, it is later compared between the old priority and support capability with the new one according to the class interval.

Class interval value and watershed support capability categorization
The value criteria to determine the watershed classification according to its support capability in Indonesia covers 5 criteria and 15 sub-criteria [13,14] e.g. the land condition (40%), water system (20%), socoeconomic (20%), building investment (10%) and space utilization (10%), with total value ranging from 50 to 150 (see table 1). Watershed support capacity assessment in each class or class total, for every criteria and sub-criteria, consists of 5 scoring categories from very good, good, fair, poor, to very poor. The range value (R) is 100, counted from the highest (150) minus the lowest (50). The length or class interval score is 20, resulted from the division of 100 as range value (R) and 5 as the category value. From the mentioned calculation, the Class Interval Score and Watershed Support Capability are gained (see table 2).

Watershed classification criteria toward watershed support capability value
In accordance to Indonesia Governmental policy, Permenthut number 60 in 2014 established the criteria of watershed classification, with the purpose of being used as the guidelines or reference for the related institutions in managing the watershed development in order whether to maintain or to recover the watershed support capability. Basing on the Interval scores and the watershed support capability for future development, it is needed to classify these data into 3 categories: one prioritized to maintain its support capability (Very Good and Good), one needed to be improved (Fair), and one that needed its support capability to be recovered (Poor and Very Poor), as can be seen in table 3 below.  From table 3, it can be seen that the watershed classification of "Improved" is the threshold or the unstable (critical) class, in which if the value decreases even for a bit then that class will face a change to its worse condition, and if the value increases then the condition changes into a better one.

Prioritized scale determination in watershed management
According to governmental policy Permenthut number 60 in 2014, the result of watershed classification criteria does not meant to be used as the basis for determining which forest and land rehabilitation technique, nor the water resource development technique to use. Yet it is expected to give an illustration of how dire the urgency in managing the watershed in national, province, and even regency/city area scale. The Indonesia government, in watershed management issue, has established 2 (two) Watershed Classification toward its support capability, if the value (Watershed Support Capability <100) then that watershed is maintained and if the value (Watershed Support Capability >100) then that watershed needs its support capability to be recovered. These assessments do not vividly show the urgency level in neither managing the watershed nor referring to the class interval score and the category. Presented below is the watershed classification according to the current watershed support capability (Table 4). Whereas the priority scale determination in accordance to the current support capability situation can be seen at Table 5, in which the interval score does not refer to the class interval. Since the urgency level (priority scale) is important in the establishment of watershed management, so it is needed to have the criteria to set the urgency level (prioritized scale) that will be used as the basis of determining the next concrete steps to be done according to established urgency level. As an effort of development, I present 2 (two) urgency level (prioritized scale) of watershed cultivation management. Scheme A (first) is divided into 3 (three) urgency levels which are the priority scale III (Maintained support capability watershed), priority scale II (Improved support capability watershed), and priority scale I (Recovered support capability watershed).

The priority scale application on gangsa watershed
The criteria used to determine the Gangsa watershed [13,14] [13,14]. According to the class criteria and assessment criteria applied at Gangsa watershed, it can be generated that the result of support capability condition is as following. Gangsa watershed support capability condition has the value of 106, consists of Land Condition criteria: Critical Land Percentage (10), Vegetation Coverage Percentage (12.5), Erosion Index of 10, in total 32.5. Meanwhile the water system condition consists of the Flow Regime Coefficient 7.5, Annual Flow Coefficient (C) 7.5, Sedimentary Content (SC) 6, Flood in score 3, while Water Use Index (WUI) is 5, in total 29. As for socioeconomic condition, the Residents' Density in 10 points, Residents' Welfare at 7, Norm Existence and Enforcement is 3.75, in total 20.75 points. For Building investment criteria, it consists of City Classification at 6.25 and Building Value at 7.5, in total 13.75. The last criteria is Space Utilization, which are the Protected Area at 7.5 and Distinguished Area at 2.5, in total score 10.
The new watershed classification assessment (observing the class interval) is divided by 3. The Maintained classification is applied if the score is between ≤ 50 to ≤ 90. The Improved classification is applied if the score is between > 90 to ≤ 110. The Recovered classification is applied if the score is between > 110 until ≤ 130. Whereas the older watershed classification (one that does not pay attention to the class interval), the support capability is divided into 2 (two) watershed classification, which are the Maintained if the support capability lies on ≤ 100 (Good to Very Good category) and Recovered if the support capability is > 100 (Poor to Very Poor).
According to the analysis result, Gangsa watershed support capability is 106. In accordance to the old priority scale, Gangsa watershed belongs to Priority III for its support capability and rated as Recovered. This assessment is unsuitable with the actual condition. Hence, it is needed to evaluate more about the watershed classification application by adding more thresholds or support capability categories. By using the new watershed support capability standard (the developed results), Gangsa watershed classification according to its support capability in scheme A is rated as Priority II, and according to scheme B it is rated as Priority III with classification: Improved. If compared to the interval class (the developed one) with the older classification (current situation), this Gangsa watershed undergoes a change in classification from Recovered to Improved.

Conclusion and advices
management according to the support capability, the urgency level is counted into the Priority II (Scheme A) and urgency level in Priority III (Scheme B).