Potential of Hydropower-Based Renewable Energy in Cipunegara Watershed

Developing new and renewable energy (NRE) is a sustainable solution to the current complexity associated with population growth and environmental problems. Some developed countries have recognized renewable energy development as a substitute for non-renewable energy such as coal, petroleum, and natural gas. Therefore, this study employed the geospatial approach scheme to identify the NRE potential in the Cipunegara watershed. This was achieved using regional research with a spatial approach and considering five locations in the upstream area of the Cipunegara watershed. Data were collected through observation, consultation with experts, and map interpretation, and analyzed using descriptive statistics. The results showed that only location 2 had a significant potential to be used in building a dam to generate electrical energy. This study was based on several aspects such as hydrology, morphology, topography, meteorology, erosion, geology, and land use. The results were derived from empirical data and geospatial modeling, and expected to serve as a significant reference for the central government in developing EBT as the tangible manifestation of the Sustainable Development Goals 2030 program and the implementation of the national research master plan 2017-2045.

Some of these programs were designed to meet daily needs.Moroever, an increase in population can lead to a higher demand for water to meet food and humand needs.This means food and human activities are closely related to water (Akhirul et al., 2020;Setiacahyandari et al., 2022;Sitompul & Efrida, 2018).However, the current problem is that most energy are generated from the depleting non-renewable fossil fuels, thereby requiring humans to find renewable energy sources (Shiva Kumar & Sudhakar, 2015;Tang et al., 2017).
Hydropotential is generally usually used to satisfy only household and irrigation needs despite its ability to function as a renewable energy source, specifically to generate electrical energy (Syahputra & Soesanti, 2021).Therefore, this study focused on identifying the potential of hydropower as a renewable energy in Indonesia using geospatial and empirical approaches.The process involved highlighting several track records in the country, specifically in the Cipunegara watershed, such as the study conducted to determine the estuary changes in Cipunagara and Cimanuk Rivers using landsat imagery spatial analysis (Nur et al., 2020), and characterization of hydrocarbon reservoirs in Ozara Field, North West Java Basin using acoustic impedance inversion analysis (Zacky, 2020).
NRE was observed to have been developed in several countries using different models.An example of this is the study conducted in Turkey which used hydroelectric power plants on the carbon emission resulting the 408,533.57tCO2 fossil sources per year produced from the dam reduced carbon footprint (Bayazıt, 2021).Another study reported that hydropower was the leading renewable energy provider while solar and wind power were at the infant stage.This was confirmed by the findings of the survey conducted in 2019-2020 that the hydropower contributed 66,216 MW to the 1,53,888 MW renewable energy capacity of South Asia (Mitra, et al. 2023).
The development of NRE is considered urgent due to the prevalence of climate change problem in the global community.Most relevant studies did not focus on identifying the potential for hydropower renewable energy, specifically in the upstream area of the Cipunegara Watershed, West Java.Moreover, attention has been placed on renewable energy potential using literature and empirical studies but only a few applied geospatial and empirical elaboration modeling.Therefore, this study was conducted to identify and analyze hydropower-based renewable energy potential by reviewing several aspects such as hydrology, morphology, topography, meteorology, erosion, geology, and land use using the combination of geospatial and empirical modeling.

Study Area
This study was conducting by incorporating a spatial approach in survey and this means the analysis focused on the inclusion of spatial variables in the study area (Yunus, 2016).This study was conducted in the upstream area of the Cipunegara watershed located in the administrative area of Subang and Sumedang regencies, West Java, Indonesia.The specific information on each location point is indicated in the following Figure 1.Moreover, the samples used were determined based on areal-based sampling technique while regional engineering was applied to examine the physical and cultural components (Yunus, 2016).Several observation points were selected based on practitioner studies as described in the following Table 1.Five locations selected for this study were in line with the target of the government in line with the recommendations made during the specific working visit of Commission V of the House of Representatives of Indonesia to Subang Regency, West Java Province at the second session of the 2021-2022.The Commission proposed the construction of Cipunegara Dam to overcome floods in Subang and Indramayu Regencies in addition to some other functions.The upstream area was observed to be physically suitable for dams based on hydrological, morphological, topographic and other assessments conducted.

Data Collection Techniques
Data were collected through the techniques adapted from Yunus (2016) and explained as follows: Observation was applied to (1) non-human or non-living objects such as rivers, soil, geological layers, and geomorphological structures as well as (2) artificial non-human objects such as settlement complexes, rice fields, and others.Consultation with Experts was implemented to identify the locations used as samples as well as to identify areas with hydropower-based renewable energy potential.Map Interpretation was utilized to determine specific potential locations using several geospatial models to study certain aspects.

Data Analysis
The data obtained were analyzed using quantitative descriptive analysis techniques.The process involved applying a spatial approach with geospatial technology in the form of ArcGIS to identify the feasibility of potential locations for hydropower-based renewable energy.The scheme for the analysis is presented in the following Figure 2 with the due consideration of professional studies conducted by water resources management consultants.The parameters used are also specifically described in Table 2

RESULTS AND DISCUSSION
Geospatial modeling scheme supported by empirical data obtained from surveys was used in this study and described as follows:

Renewable Energy Potential based on Hydrological Aspects
Cipunagara watershed is geographically located between 83º 12ꞌ -82º 41ꞌ S and 127º 23ꞌ -130º 57ꞌ E with a tropical climate and administratively placed in three regencies including Subang, Indramayu, and Sumedang.The main river in the watershed is Cipunagara with a total length of ± 104 km and an average width of 40 m.Its springs are located in Bandung Regency, precisely at the foothills of Mount Tangkuban Perahu (2,706 m a.s.l.), while the downstream is mainly in the Subang Regency area (Sunarko, 2021).
The watershed is elongated with a catchment area of 1,203 km 2 in the form of mountainous areas in the upstream and relatively gentle heights in the downstream used for rice fields (agriculture), gardens, settlements, and trades.Administratively, it is mostly bounded by Subang Regency with the Java Sea in the north, Subang in the west, Indramayu in the east, and Sumedang and West Bandung in the south (Sunarko, 2021).The geometric parameters of the watershed were measured and the results are presented in the following Table 3.The specific hydrological parameters observed at several locations are also indicated in Figure 3.Moreover, this aspect covered the width of the catchment area as indicated in the geospatial data presented in the following Table 4.The eligibility criterion was that a wider catchment area would produce more discharge (Nurhamidin et al., 2015).Some observer practitioners also argued that a larger catchment area could accommodate a large water scale.This was further supported by dendritic patterns observed in the five points studied which were considered suitable to serve as inundation for the dam body.It was also discovered that some of these aspects were only a tiny part of the NRE potential assessment scheme.Therefore, an in-depth investigation was suggested to have a better overview.

Renewable Energy Potential based on Morphological Aspects
The morphological aspect was reviewed using a geospatial approach based on Van Zuidam (1983) criteria.An empirical method was also applied to identify prospective reservoir dikes.Moreover, some practitioners proposed that the standardization of feasibility for the morphological aspect of constructing a dam is in the undulating and steep hilly areas such as natural dikes.The data recorded from the observation points are presented in the following Table 5.The locations identified and analyzed in the preliminary feasibility study are presented in the Figure 9.This initial morphological feasibility was considered important in the process of planning a dam construction.The phenomenon was attached to the relationship between water availability and the physical conditions of an area such as the morphology, bulk, as well as the natural processes in the water cycle of the watershed (Zarkasih, 2018).Furthermore, several locations reviewed through an empirical approach indicated the potential for the implementation of levee construction.The observation data retrieved during the process are presented as follows:

"Observation point 4 indicated that the appearance of two hills (A & B) as embankments was sufficient to meet the feasibility standards because the elevation was high enough to build an embankment dam." (Results of Practitioner Study, 2023) "Observation point 5 showed that the appearance of two hills (A & B) as embankments was sufficient to meet the feasibility standards because the elevation was high enough to build a reservoir embankment." (Results of Practitioner Study, 2023)
The empirical results of the survey conducted in the five selected locations showed that locations 2, 3, 4, and 5 were considered suitable for natural dam embankments.Location 2 was found to be very feasible because of its steep elevations and the ability to reduce the cost of constructing the dam.Meanwhile, Location 1 was discovered to be unfeasible due to its slope morphology and absence of hilly terrain to be used as a natural embankment for the dam.

Renewable Energy Potential based on Topographic Aspects
The investigation of the topographic conditions is very important in the process of planning the construction of an embankment dam.This was associated with the their ability to predict and validate the potential breakdowns for the dam (Aureli et al., 2022) and serve as a model scheme to determine the influence of topographic form on dam behavior (Tian et al., 2021).The topographic conditions are also essential in determining the stability of landslide dams (Wu et al., 2020).They can further be incorporated with the morphology of the area to model the depositional projections and internal structure of a dam (Zhou et al., 2019).The topographic reviews conducted through the observation of the locations as part of the preliminary assessment to plan the embankment dam construction are presented in the following Figure 10.The geospatial scheme modeling investigation was used to show the priority of feasibility standards at Location 2. According to the information retrieved from practitioner studies, the location had two natural hills that met the feasibility standards and this could reduce the cost to be incurred by the central government in constructing the dam on a location with similar characteristics (Results of Practitioner Studies, 2023).This was reinforced by the extensive results obtained from the initial investigation in Table 6.

Renewable Energy Potential based on Meteorological Aspects
Rainfall data have been used by several stakeholders for different purposes such as agriculture, irrigation, transportation, industry, tourism, and others.This is in addition to its utilization in some other specific situations such as the management of dams (Rohmat & Setiawan, 2019).Moreover, accurate rainfall-runoff modeling was considered fundamental to the planning and management of water resources such as drinking water, agriculture, industry, hydropower, and others (Hidayah et al., 2022).This is the reason geospatial modeling was applied to each location and the results are presented in the following Figure 11.Meteorological reviews in the form of average annual rainfall are one of the primary considerations in designing water reservoirs.This was further confirmed by some studies that rain needs to be modelled into flow discharge to determine the potential of water resources in a catchment area (Sitanggang et al., 2014).Numerical rain analysis was observed to have been conducted to determine the rain intensity in a catchment area (Rasyid et al., 2023).However, the percentage of NRE potential was determined in this study through geospatial modeling analysis using ArcGIS and AutoCAD software as presented in the following Table 7.The information obtained from the practitioner studies indicated that the five locations observed had the rough potential and feasibility to be used for dam construction.This was further reflected in some numerical calculations concerning several aspects.Moreover, the standardization of rain numeracy feasibility was required to be determined on a minimum time scale of 10 years (Results of Practitioner Studies, 2023).

Renewable Energy Potential based on Erosion Aspects
The erosion aspects were reviewed to project future sedimentation.This was considered necessary because sediments have the ability to cause hydropower dam failure (Salau & Ifabiyi, 2019).The treatment of sedimented areas usually require high budgets in addition to the impacts on sustainability in the form of eutrophication in dam areas.This led to the implementation of numeracy scheme modeling to identify erosion rates in catchment Areas using the formular designed Julien (2010) which involved predictions through the Universal Soil Loss Equation (USLE) approach.The number of erosion rates per year needed to be determined due to its influence on the quality of dam infrastructure (Results of Practitioner Studies, 2023).The erosion rates calculated at each observation point are presented in the following Table 8.The specific information on the erosion rates is indicated in the following Figure 12.The erosion rate projections and geospatial modeling schemes showed that the third and fifth locations had the most significant erosion rate volume compared to the other others.Meanwhile, feasibility assessment rarely recommends a site with a high erosion rate for dam construction.

Renewable Energy Potential based on Geological Aspects
The review of the geological aspects was considered important in the process of planning dam construction for micro-hydro-based renewable energy due to the detrimental impact of constructing in an improper area such as the existence of leaks in the dam body (Results of Practitioner Studies, 2023).Therefore, the results of the geospatial modeling in each location are presented in the following Figure 13.

Renewable Energy Potential based on Land Use Aspects
The land use aspect is usually considered as the final stage of determining the appropriate location for dams.This was linked to the fact that the socio-cultural condition of the community was considered one of the variables to ensure smooth dam construction by practitioners in physical studies (Results of Practitioner Studies, 2023).The construction of dam in Indonesia was required to focus on this aspect because the country has different beliefs based on tribe and culture.Furthermore, compensation to be given to the users of the land needs to be evaluated due to the limited budget provided by the stakeholders for land acquisition.The results obtained for each location are presented in Figure 14.
The land use area for each location specifically identified through geospatial modeling is presented in the following Table 10.Land-use review is normally the final aspect of the rough planning for the construction of dams.It is considered important due to the need to obtain land turnover and residents' approval to construct water infrastructure like dams.In this study, several locations were categorized as suitable for dam construction but it is necessary to consider the approval needed and the compensation fee to be paid to the surrounding communities.An area with more residential land required a higher budget but the area owned by the central or regional government was confirmed to need lesser budget (Results of Practitioner Studies, 2023).The elements existing on the site were also discovered to be influencing the construction feasibility.For example, sacred sites cannot be moved, thereby making the construction of dams to be difficult while some other elements can be shifted to the planning area.This aspect is considered important due to the need for the planners to understand the culture and beliefs of the affected communities during the planning and implementation phases.Moreover, it is impossible to implement the plans when there are discrepancies in the social-cultural aspect even though all the physical aspects met the feasibility standards for dam construction (Results of Practitioner Studies, 2023).The observational studies conducted based on the modeling results and practitioners' considerations led to the summary presented in the following Table 11.

Figure
Figure 1.Study Area

Figure 2 .
Figure 2. Scheme of Data Analysis of NRE Potential (DAM)

Figure 9 .
Figure 9. Observations based on Geomorphology Aspects

Figure 10 .
Figure 10.Observations based on Topographic Aspects

Figure 11 .
Figure 11.Observations based on Meteorological Aspects

Figure 12 .
Figure 12.Observations based on Erosion Aspects

Figure 13 .
Figure 13.Observations based on Geological Aspects

Figure 14 .
Figure 14.Observations based on Land Use Aspects

Table 1 .
Observation Points to determine Hydropower-Based Renewable Energy Potential

Table 2 .
. Geospatial Modeling Parameters of Hydropower-Based NRE Potential Measurement

Table 3 .
Geometry of Cipunagara Watershed

Table 4 .
Width of Catchment Area

Table 5 .
Land Area by Morphology

Table 6 .
Land Area by Slope

Table 7 .
Percentage of Renewable Energy Potential

Table 8 .
Erosion Rates Calculation

Table 10 .
Land Use Area of Observation Location