2020 International Conference on Sustainable Energy Engineering and Application (ICSEEA)
Watershed Management for Micro Hydropower Plant Sustainability: Malabar, Indonesia
Yuliana Susilowati Research Center for Geotechnology
Indonesian Institute of Sciences Bandung, Indonesia
Pudji Irasari
Research Centre for Electrical Power and Mechatronics
Indonesian Institute of Sciences Bandung, Indonesia
Yugo Kumoro
Research Center for Geotechnology Indonesian Institute of Sciences
Bandung, Indonesia [email protected]
Wawan Hendriawan Nur Research Center for Geotechnology
Indonesian Institute of Sciences Bandung, Indonesia [email protected]
Yunarto
Research Center for Geotechnology Indonesian Institute of Sciences
Bandung, Indonesia [email protected] Abstract— The purpose of this research is to analyze the
watershed management system for the sustainability of hydropower plants. The two main parameters needed to produce electrical energy are water flow and head. Water flow depends on the watershed area, rainfall, and land cover, which affects the runoff and infiltration volume. Good land cover has a large infiltration volume so that it can infiltrate rainwater into the ground and become the reserved water to maintain base flow during the dry season. Malabar Micro Hydropower Plant (MHP), Bandung, West Java, Indonesia, was selected as the case study. There are no significant land-use changes in this area resulting in a stable base flow, which allows MHP to work well until now. The base flow can be continuously maintained at a value not less than 3 m3/s, the same as the designed discharge of the power plant. The land-use changes are possible as long as the flow is not lower than the minimum base flow. It can be employed by using a high infiltration coefficient of land cover and artificial recharge groundwater techniques..
Keywords— watershed management, micro hydropower plant, sustainability, water flow, artificial ground water recharge.
I. INTRODUCTION
The utilization of a hydropower plant will reduce dependence on fossil energy and reduce the amount of carbon emissions. This is very important to preserve the environment and make life healthier [1]–[6].
The hydrological conditions and topography of Indonesia with the mountainous region and the land cover in the form of tropical forests have the potential for abundant hydro power.
The mountainous conditions produce many streams of waterfalls with large differences in height. The land cover condition in the form of tropical forest makes it possible to produce rivers with stable water flows, without experiencing a significant difference during the rainy season compared to the dry season [4], [7]–[13].
Land use and land cover changes will result the changes of soil infiltration rate. A sufficient amount of water infiltration is needed to fill the groundwater basin which is a mainstay of discharge supplies during the absence of rainfall in dry season.
Land use changes need to be maintained so that the infiltration characteristics of the watershed have an infiltration volume
that is sufficient to maintain water flow according to the MHP needs at that location [14]–[19].
Mekong watershed management is discussed in [20]. This study aims to determine the impact of MHP development on social, economic and environmental aspects. The results showed that the community felt many benefits from MHP development and the watershed provides critical environment.
Another study implemented a spatial model to learn the effect of the upstream land use alteration to the quality of water flowing to hydropower stations in Bhutan [21]. Spatial models were connected to a system model with social and economic variables to guarantee connections between hydropower and socio-economic development were taken into account to establish more rational land use scenarios.
In reference [22], upper watershed management is carried out to overcome reservoir sediment by applying the Soil and Water Assessment Tool (SWAT) interfaced with MapwindowGIS to model and predict sediment yield and concentration into the subbasins of the upper watershed of Kainji hydropower dam in Nigeria. This method is able to reduce sediment yield and concentration by 37% and 34%
respectively.
This paper will analyze the watershed management system for the sustainability of hydro power plant. Malabar MHP, located in the Malabar Tea Plantation, Bandung, West Java, Indonesia was selected as the case study area. Malabar MHP has been built in 1941, since the Dutch colonial era. The MHP was built to meet the electrical energy needs of the tea factory.
Malabar MHP has been operating for more than one hundred years, was selected as a case study for this research.
Until now, Malabar MHP is fully operational with the full capacity.
The existing land cover of Malabar watershed area are dominated by forest and tea plantation. Until now, there are no significant land use changes in the Malabar watershed area.
The watershed management of Malabar MHP have enabled the power plant to operate well until now. Watershed management is a major part of MHP’s operation and maintenance, to ensure the availability of water flow needed to turn the turbine of the MHP.
II. MATERIAL AND METHOD A. Study Area
Malabar MHP is an outlet of Cilaki watershed (Fig 1). The Cilaki River is a tributary of the Citarum river, its upstream lies in Kendang Mountain Bandung District, West Java Indonesia, the water flows to the west and unites with the Citarum river which empties into Muara Gembong, Bekasi District, West Java Indonesia.
Fig. 2 exhibits the layout of the MHP components comprise of a weir, intake, waterway, penstock, and powerhouse, while Fig. 3 illustrates the water flow of the Malabar MHP of 3 m3/s. The height of the Malabar penstock is 100 m (Fig. 4) and the powerhouse is located in the site with low risk from floods and landslides hazard (Fig. 5). The
turbines and generators used are the original machines that were installed since the first time they were built (Fig. 6). For more than 100 years of operation, the Malabar MHP has routine maintenance and minor repairs.
B. Hydrological Analysis for MHP
There are several methods for utilizing river flow to generate electricity. The most common way is to use a dam, especially for large-scale generation. It can also take the flow from a high point and divert it to an open or closed channel, or penstock pipe, then flow it back into the river, called a run- of-river hydropower plant. It is usually employed to small and micro hydropower to avoid impact on the environment.
Natural river flow can also produce electric power by applying hydrokinetic turbines.
Fig. 1. Study area, Malabar tea plantation, West Java, Indonesia
Fig. 2. Malabar micro hydropower plant component layout.
Fig. 3. Water flow of Malabar MHP
Fig. 4. Penstock of Malabar MHP
Fig. 5. Power house of Malabar MHP
Fig. 6. Generator of Malabar MHP
The hydrological study aims to learn whether the available water discharge and plunge height can drive the turbine according to the desired power (3 x 700 kW), which is the existing power plants. The hydropower potential study includes measuring the minimum discharge flowing in a water channel/river, water discharge during a flood, and available waterfall height (height difference).
Hydropower schemes, in general, may have [23]:
• Several water intakes to collect water,
• A settling basin to filter out garbage, dirt and sediment carried by the flow.
• One or more penstocks for conveying water to the turbine,
• Excess water channels and other uses channels.
• A powerhouse for a power plant, which contains one or more sets of turbine-generators,
• A tail race outlet.
The equation of hydropower energy is [3]:
ܲ ൌ ߟ ή ߩ ή ݃ ή ܳ ή ܪ (1)
ܳ ൌ ݒ ή ܣ (2) where P = hydropower output (W) ρ = water density = 998
kg/m3, g = gravitation = 9.81 m/s2, Q = debit (water flow) = m3/s, H = net head (m), η = system efficiency (assumed to be 0.7), v = flow rate (m/s) and A = cross-sectional area of the flow (m2).
Parameters for calculating water flow consist of rainfall, catchment area, and type of land cover in the catchment area.
Water flow is obtained from the equations:
ܳ ൌ ሺͲǤͲͲʹͺܥݓݏݔܫݔܣሻ ܾ (3) and
ܥ
௪௦ൌ
σσసభ
సభ (4)
where Q: the water flow (m3/s), Cws: the runoff coefficient (depend on the land cover/land use) , I: the rainfall (mm/hour), A: the watershed area (ha), Ai: the land area with land cover type i, Ci: the runoff coefficient of the ground cover type i, n:
the number of land cover types and b: base flow.
The availability of water resources in a watershed is determined by its hydrological characteristics. The characteristics of rainfall and runoff in a water catchment are hydrological cycles, which are influenced by geological factors, flow patterns, soil and land cover. The available water in the area is divided into surface runoff, interflow and groundwater recharge flows.
River flow consists of quick flow and base flow. Quick flow originates from the surface runoff and base flow originates from shallow and deep groundwater. In tropical areas, the base flow is less affected by rainfall but is influenced by the release of groundwater. Base flow will be influenced by natural factors such as climate, geology, relief, soil and vegetation. Human activities that cause changes in landscape and land cover can lead to changes in the above factors and can ultimately affect the timing and quantity of base flow.
Watershed management is needed to maintain the stability of flow characteristics. Changes in land cover and land use greatly affect the runoff characteristics and infiltration volume of a watershed, which in turn affects the availability of surface water and groundwater in the area. Land cover is a major factor affecting infiltration characteristics and affecting subsurface water storage and base flow. Changes in land cover will result in changes in the characteristics of the inflow, increase the volume of flooding in the rainy season and increase drought or decrease the discharge in the dry season.
C. Remote Sensing Application
In this study, remote sensing is applied to determine the condition of land-use, land-cover, geological aspects and to estimate the potential magnitude of hydro power. Land use and land cover will be analyzed to find out why MHP Malabar can operate at full capacity for about 100 years, while geological aspect analysis will be used as a reference in determining the layout of MHP components by considering the smallest disaster risk.
Land cover refers to the physical and biological cover over the surface of the land, including water, vegetation, bare land, and/or artificial structures. Land use relates to human activities such as agriculture, forestry, as well as build up area.
Land cover can be observed directly in the field or based on interpretation of remote sensing data. Land use is an integration between land cover conditions and socio- economic activities on the land. Different land uses can have the same land cover. On the other hand, the same land use can have different land cover. The land use map was interpreted based on the land cover identification of remote sensing data.
This study deploys Landsat 8 Operational Land Imager (OLI), acquired on 20 June 2020. The data was used for Land use, Geology, and Landslides mapping. Land use mapping was carried out using a combination of band 5 (Near Infra-Red / NIR), band 4 (Red), and band 3 (Visible Red). The Landsat 8 OLI was extracted to enhance the land cover features. Bands 5-4-3 (NIR, Red, and Green) are extracted and mapped into red, green, and blue (RGB color). The combination of certain bands can classify the features of the classes, such as water, vegetation, and built-up area.
III. RESULTS AND DISCUSSIONS A. Hydrologycal Analysis of Malabar Watershed
Malabar MHP is located in the Cilaki river outlet. The Cilaki River flows along 20,180 km and has a watershed area of 8,170 ha (Fig. 7). The land cover of Malabar watershed area are forests and tea plantation (Figure 8). There are no significant land use changes in the Malabar MHP watershed since 1941, when the Malabar MHP was built, until now.
The Malabar watershed area is entirely composed of volcanic activity products. Mt. Kendeng at the north-west end is an old volcano with cranial remains on it, mostly in the form of pyroclastic deposits (Fig. 9). The southeast part is the eruption product of Mt. Patuha, a white crater that is mostly lava. The eastern part is the product of the eruption of Mount Malabar, which consists of domes, lava flows, and pyroclastic deposits caused by different processes. The volcanic complex is indicated by the Mt. Tilu complex to the east of Mt. Kasur as well as Mt. Tanjaknangsai and Mt. Lamajang complex to the west of Mount Malabar. The rest consists of old volcanic rock groups whose source cannot be determined. In the
Malabar watershed area, there are several lineament features recognized from the satellite image interpretation. The lineament of the geological structure is an indication of a
geological fault. It is highly susceptible to hazards of landslides and earthquakes and should be avoided for the development of MHP components.
Fig. 7. Malabar watershed of Malabar micro hydropower plant Source: Data interpretation based on Rupa Bumi Indonesia (RBI) topographic map.
Fig. 8. Land use map of Malabar watershed. Source: Data interpretation based on Landsat 8 Operational Land Imager (OLI), acquired on 20 June 2020.
Based on the interpretation of satellite image data, several locations have the potential for landslide hazards in the Malabar watershed area, shown as the red areas in Fig. 10.
Landslides in the image are characterized by the landslide
crowns, steep walls of topographic valleys, and different rivers from the surrounding slopes. Moreover, river valleys that are steep in soft and unstable rock types are potential landslide zone.
Fig. 9. Geological map of Malabar watershed. Source: Data interpretation based on Landsat 8 Operational Land Imager (OLI), acquired on 20 June 2020.
Fig. 10. Landslide map of Malabar watershed. Source: Data interpretation based on Landsat 8 Operational Land Imager (OLI), acquired on 20 June 2020.
Understanding the hydrological cycle, including surface and groundwater flows, is essential in planning water resource management. Direct flow is a direct response to rainfall events, including surface runoff (runoff) and lateral flow in the soil profile which is also known as interstellar flow. Base flow is a component of river flow originating from natural aquifer reservoirs. The increase in base flow occurs in areas that have land cover with high infiltration efficiency so that they have a high infiltration rate in filling the ground water aquifer.
To achieve a sustainable MHP, the condition of land cover must be maintained. Hydrological function of watershed is the response of an area to rainfall and surface runoff. A watershed has a good hydrological function if the fluctuation of runoff flow due to rainfall is small and availability of flow during the dry season can be maintained. The hydrological function of watershed can be measured from the value of the Base Flow Index (BFI). The BFI is one of the most important base flow indices, which is the long term ratio value between the base flow and the total flow in a certain period of time continuously and is influenced by a number of climatic and topographic factors.Land cover in the form of forest has the ability to absorb water into the soil properly. This becomes groundwater reserves and becomes a mainstay of flow when there is no rain.
Forest land cover has a high infiltration capability so that it can maintain the stability of water flow fluctuations, there is no large difference in water flow between the rainy season and the dry season. The stable water discharge will ensure MHP continues to operate even in the dry season and does not endanger MHP construction during the rainy season.
If there is a land use changes, it is necessary to consider the type of land cover and plants that are able to maintain the volume of water flow according to the MHP requirements.
The Malabar MHP designed flow is 3 m3/s. Land use changes on the ctachment of the MHP location, from tea plantations to other more economical uses are possible as long as it takes into account the capacity of the land to absorb water into the soil. If the change in land cover causes the hardening of the land to become a permeable surface, then water infiltration engineering can be carried out using various methods such as the artificial ground water recharge technique.
B. Hydropower Output
In this research, the rainfall data was provided by the rainfall gauge station data belonging to PTPN VIII Tea Plantation. Rainfall data is the annual rainfall obtained from measurement data from 1998 to 2015 (Fig. 11). The annual rainfall of the Malabar watershed ranges from 1900 – 3700 m3/year. The results of water flow measurements at the Malabar Watershed outlet in 2011-2015 range from 3.55 m3/s to 3.87 m3/s. This volume base flow is sufficient for the needs of Malabar MHP, which is 3 m3/s.
The land use of the Malabar watershed was divided into four classes, which are forest, tea plantation, built-up land, and bare land. The runoff coefficient values are listed in Table I.
The existing land-use of the Malabar watershed has a runoff coefficient of 0.31, produces 3.87 m3/s water flows.
From the calculation above, it is determined the potential water flow of Malabar MHP is 3.78 m3/s and the potential head is 101.32 m. By taking 80% of each of those values, the water flow design is 3 m3/s, and the head design is 100.80. The potential hydropower output is 2,373 kW, and the designed power is 2,255 kW as presented in Table II. The results of the hydropower calculation confirm that the river flow conditions are still sufficient to operate 3 units of the generating system, each with a capacity of 700 kW.
A scenario analysis was carried out, in case of change the 39% of the tea plantation into a built-up area. The alteration changes the runoff coefficient to 0.46 (Table IV). It causes
Fig. 11. Time series data of Hydrological condition of Malabar watershed 1998 – 2015
TABLEI.MALABAR HYDROPOWER
Description Value Unit
Potential Water Flow 3.78 m3/s
Designed Water Flow 3.00 m3/s
Potential Head 101.32 m
Designed Head 100.80 m
Potential Power 2,373 kW
Designed Power 2,255 kW
changes to the runoff volume and infiltration volume, which is in reverse correlation (Fig. 12 and Table IV). This scenario results in a decrease in the base flow volume to below 3 m3/s.
Based on this scenario analysis, a 39% change in tea plantation into a built up area will reduce the volume of base flow to below the minimum water flow limit for MHP purposes. Land use changes that occur will result in MHP unable to operate and must be turned off.
Land use change is possible if it can keep the base flow volume at the minimum of MHP requirement. Maintaining base flow can be done by applying artificial ground water recharge techniques. Ground water recharge can be done by flowing water through canals at ground level, multiplying irrigation channels, infiltration ponds or by injecting directly under ground through injection wells.
The artificial ground water recharge method can be classified into two major types: (a) water dispersion techniques, and (b) well injection techniques. The water dispersion technique is cheaper than the injection well technique. In addition, water dispersion techniques can be used for the management of infiltration water in large volumes. Water dispersion techniques can also significantly improve the quality of recharge water during infiltration and during movement through unsaturated zones and receiving aquifers.
The success of the artificial ground water recharge technique requires in-depth knowledge of the physical and chemical characteristics of the aquifer system. Extensive experiments and adjustments of artificial recharge techniques are required to suit local conditions.
Fig. 12. Scenario Analysis of Hydrological condition of Malabar watershed 2011 - 2015.
TABLEII.RUNOFF COEFFICIENT OF LAND USE/LAND COVER
Land use/ Land cover Runoff coefficient (C)
Forest Land 0.10 – 0.40
Tea Plantation 0.40 – 0.50 Built-Up Land 0.50 – 0.70
Bare Land 0.70 – 0.95
TABLEIII.ACTUAL AND SCENARIO OF RUNOFF COEFFICIENT OF
MALABAR WATERSHED
Parameter
Actual Scenario Area
[%]
Runoff Coef.
Area [%]
Runoff Coef.
Forest 32 0.2 32 0.2
Tea Plantation 59 0.3 20 0.3
Built-Up 6 0.7 45 0.7
Bare Land 3 0.9 3 0.9
Total 100 0.31 100 0.46
TABLEIV.ACTUAL AND SCENARIO OF WATER FLOW OF MALABAR
WATERSHED
Description\Year 2011 2012 2013 2014 2015
Rainfall 2365 2405 2743 3176 2492
Total Flow 6.13 6.23 7.11 8.23 6.46
Runoff 1.90 1.93 2.20 2.55 2.00
Runoff Scenario 2.57 2.62 2.98 3.46 2.71
Infiltration 4.23 4.30 4.90 5.68 4.45
Infiltration Scenario 3.55 3.61 4.12 4.77 3.74
Base flow 3.55 3.62 3.71 3.87 3.79
Base flow Scenario 2.73 2.78 2.85 2.97 2.91
IV. CONCLUSIONS
Watershed management for micro-hydro power plant sustainability, taking the case study of Malabar MHP, has been discussed in this paper. The potential for hydropower in the Malabar River is around 2,373 kW, confirming that the water flow is still sufficient to provide for the existed power plant operation, comprised of 3 x 700 kW. Based on this research, it can be concluded that the watershed management of the study area has been carried out well as evidenced by the continuous operation of the MHP at full capacity. Watershed management of Malabar MHP can serve as a model for other areas. The land use changes is necessary to consider the type of land cover and plants that are able to maintain the volume of water flow according to the MHP requirements. If the change in land cover causes the hardening of the land to become a permeable surface, then water infiltration engineering can be carried out using various methods such as the artificial ground water recharge technique.
ACKNOWLEDGMENT
We are grateful to Ir. Yogi Subyaktyana, PTPN VIII for his supporting to this research. Thanks to Ir. Suwijanto for his constructive discussion.
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