Evaluating and Estimating the Effect of Land Used Changed On Water Quality at Selorejo Reservoir, Indonesia

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1 Evaluating and Estimating the Effect of Land Used Changed On Water Quality at Selorejo Reservoir, Indonesia Mohammad Sholichin 1, Dr. Faridah Othman 2, Shatira Akib 3 1 PhD Student, Department of Civil Engineering, Universiti Malaya, Lembah Pantai, Kuala Lumpur, Malaysia; mochsholichin@perdana.um.edu.my; mochsholichin@yahoo.com, and Lecturer, Water Resources Department, Brawijaya University, Malang East Java Indonesia 2 Lecturer, Department of Civil Engineering, Universiti Malaya, Lembah Pantai, Kuala Lumpur, Malaysia; faridahothman@um.edu.my 3 PhD Student, Department of Civil Engineering, Universiti Malaya, Lembah Pantai, Kuala Lumpur, Malaysia; atira_77@yahoo.com Abstract Nutrients are necessary for the survival of living organisms. The most important nutrient in aquatic ecosystem is typically Nitrogen (N) and Phosphorus (P). It was considered to be an important water quality concern in Konto River Basin due to a high water pollutant indication problem of reservoir Selorejo. Nitrogen and phosphorous are the two nutrients originating from inorganic and organic fertilizer that affect the reservoir water quality due to intensive agricultural farming. Increased N and P fertilizer application on the agriculture activity has larges N and P nutrient burdens to the reservoir through runoff and leaching. The aim of this study was to identify the sources of agriculture pollutants, to quantity the loads to reservoir Selorejo and to test the application of Soil and Water Assessment Tool Model. The model was calibrated using observed flow data of river collected during fieldwork. The nutrient concentration data obtained from water quality analysis in laboratory and during filed work. The annual Nitrogen and Phosphorous concentration comparison of measured and simulated on period , and than predicted of nitrogen and phosphorous at period Result simulation was underestimate with correlation as indicated by R 2 =0,61 for Nutrient and R 2 =0,78 for Phosphorous. In general, the difference of land used in the watershed would be affected to increase runoff especially for nutrient loading on reservoir. The status of water quality at Selorejo reservoir is in accordance to the government water quality regulation. Keywords: Water Quality, Land Used, and Reservoir Introduction Recently Non Point Sources (NPS) pollution has become the focus of water quality and watershed management. Primary contributors of NPS pollution are agricultural and urban runoff. Nitrogen (N) and phosphorous (P) are vital nutrient in aquatic ecosystems, but excessive nutrient loading may cause algae blooms and accelerated eutrophication that often leads to a decline in water quality and biodiversity. Watershed is ecosystems composed of a mosaic of different land uses connected by network of stream. In-stream conditions are determined by processes occurring within the watershed and cannot be isolated from of manipulated independent of the watershed. In this study, the stream network of interest drains into a single large reservoir, and the water quality in reservoir is then directly related to conditions and processes occurring within the watershed. An evaluation of the movement of certain pollutants, such as the nutrients nitrogen and phosphorous, from the watershed to reservoir should include information about land uses, soil type, geology, topography, precipitation, and surface drainage pattern. Quantities of plant nutrients that are available for transport to surface waters are influenced by anthropogenic activities. When these nutrients are present in surface waters in excessive quantities, alga population tend to experience seasonal growth blooms that may detract from aesthetic characteristics of stream and lake/reservoir and contribute to accelerated eutrophication of water bodies. Focus of this study was to identify the non-point source from agriculture and evaluation of initial 1

2 environmental condition, especially on watershed area Selorejo. Selorejo Reservoir is second biggest dam/reservoir in Brantas River Basin, East Java. In ten year periods, development of agriculture activity and land use change from forest area become agriculture and urban was intensively. This condition would be increasing nutrient load and sediment load to Selorejo reservoir. The Study Area A. Location The Brantas River basin is located in east Java province on the island of Java, Indonesia and lies between and east longitude and and south latitude. The Brantas River originates on the slopes of Mt Arjuno (3400 msl), and follows a clockwise direction through Malang and Kediri, and branching into two distributaries at Mlirip, the Surabaya and Porong river. It has a watershed area of about 11,800 km 2, stretches 320 km. The six sub basin are Lesti Basin (625 km 2 ), Konto Basin (687 km 2 ), Widas Basin (1,539 km 2 ), Brantas Basin (6,719 km 2 ), Ngorowo basin (1600 km 2 ) and Surabaya basin (631 km 2 ), as shown in Fig 1. The study area is Selorejo Reservoir that located at upper of Konto River. It has a Catchment area of 235 km 2 at dam site of Selorejo Reservoir, and maximum reservoir capacity is million m 3, with an effective reservoir capacity of million m 3, (see Fig. 2). A detail description Selorejo reservoir is presented in Table 1. Table 1. Description Characteristic of Selorejo reservoir Item Description Catchment area 240 km 2 Flood water level (FWL) 622,60 m High water level (HWL) 622,00 m Normal water level (NWL) 620,00 m Low water level (LWL) 598,00 m Dead storage level (DSL) 594,00 m Water surface area at HWL 4,00 km2 Annual discharge/year 920 m3/dt Maximum capacity 62,30 x 10 3 m 3 Effective capacity 50,10 x 10 3 m 3 Figure 1: Brantas River Basin, East Java Indonesia 4 SUBBASIN 1 Kewayangan Sub Basin Konto Sub Basin 2 (Up Stream) 3 Konto Sub Basin (Down Stream) 4 Penjal Sub Basin Figure 2: Location of the study area, Selorejo Catchment area, east Java, Indonesia B. Land Use and Soil Type Stream water quality monitoring can be used to determine the impacts from different land uses in watershed to the overall water quality. In watershed with mixed land uses (forest, agricultural and urban), stream commonly show elevated nutrient concentration (Spahr and Wynn, 1997). Typically one of the highest sources of nutrient in the Selorejo watershed are the agricultural areas, this is due to the application of fertilizer/pesticides and disturbance of soil for agricultural production purpose. 2

3 The land use categories in the Selorejo River Basin were development using satellite imager. Land use information was collected using Global Positioning System (GPS) equipment and transferred to GIS using Arc View software (ESRI. 2004). Five land use type were considered: urban area, dry field, rice field, mixed-dry field and Forest, as shown in Fig. 3. This land use map base on the condition of 2000 year. Land used data of the 2005 condition as show as figure 4. 4 Land Use Selorejo Cacthment 2 Urban Area 3 Dry Field 4 Rice Field 5 Mixed - Dry Field 6 Forest Selorejo Sub Basin Legend!. outlet River Selorejo Dam Figure 3: Land use map of Selorejo Catchment area, base line on 2000, east Java, Indonesia Figure 4: Land use map of Selorejo Catchment area, base on 2005, east Java, Indonesia Base on land use map for condition 2000 and 2005, it shown than land use/cover should be changed for six years period. The distribution of land use changes is presented in table 2. Table 2. Proportional land use changes ( ) in Selorejo Catchment area in km 2 Land use Change (%) Urban Area Forest Dry Field Mixed Dry Field Rice Field Total (km 2 ) Dry field area decrease from 36,35 km 2 at year 2000 to 5,06 km 2 at year Mixed-Dry field area decrease from 30,01 km 2 at year 2000 to 21,43 km 2 at year But The rice field area increase from 55,51 km 2 at year 2000 to 97,01 km 2 at year According to secondary data and analysis on field work, the mixed-dry field become rice filed by farming activity for five years was slowly. 3

4 The prediction of land use map on 2010 condition, as shown figure 5. The distribution of land use changes ( ) is presented in table 3. Legend!. outlet River Selorejo Dam Soil Type REGOSOL GRUMOSOL MEDITERAN ANDOSOL Figure 6: Soil Type distribution map of Selorejo Catchment area, east Java, Indonesia Figure 5: Prediction of Land use map of Selorejo Catchment area at 2010, east Java, Indonesia Table 3. Proportional land use changes ( ) in Selorejo Catchment area in km 2 Land use Change (%) Urban Area Forest Dry Field Mixed Dry Field Rice Field Total (km 2 ) The Selorejo Catchment area has four soil types; Regosol, Grumusol, Mediteran, and Andosol, as shown in Fig. 6. And distribution of soil type is presented in table 4. Table 4. Distribution of Soil Type in Selorejo Catchment area Soil Type Area (km 2 ) % Total Regosol Grumosol Mediteran Andosol Total (km 2 ) % C. Sources of Pollutants Water quality monitoring for nutrient requires accurate of stream surface water velocity. For this reason the sampling method, frequency and analysis are some of the principal factor to consider for constituent loads determination. Due to the negative impacts that excess of nutrient can cause to water bodies (eutrophication) it is important to determinate concentration, trends and loads of these pollutants and associates then to possible contributors (NPS or PS). To exactly determinate of Nutrient load is difficulty. Several methods can be applied for this purpose like, interpolation, regression and average techniques. The primary water pollutant load in study area was two categories, first from Agriculture area and second from urban area. According from Department of Agriculture Malang-East Java data, commonly farmers in study area using fertilizing with Urea (Ca(NH 2 ) 2 ); TSP 4

5 (Ca(H 2 PO 4 ) 2 ); KCL and ZA. (see Table 5). Farmers on the site study use much fertilizer and pesticides more than normal regulation. Wastewater from urban area was calculated which assumed that human faces contain 14,5 g.n/day/person;1,9 g.p/day/person and Urine contain 7 g. N/day/person, 2 g.p/day/person. (Dyah, R., 2002, ) Table 5. Using fertilizer for each plant. Plant Fertilizer (kg/ha) Urea TSP KCL ZA Rice Corn Soybean In the study area, water monitoring gauge/discharge gauge have been build in Konto River and Kewayangan River. From each gauge, discharge and concentration (N, and P) were collected for five years ( ). (See Fig 7.a and 7.b) Discharge (m3/dt) Average Monthly Discharge Inflow & Outflow at Selorejo Outflow 2003 Inflow Figure 7a. Monthly average discharge inflow & outflow at Selorejo reservoir. N & P (mg/l) Phosphorous Nitrogen Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03 Jan-04 Jul-04 Jan-05 Figure 7.b. Monthly average of Nitrogen and Phosphorous Concentration at Selorejo reservoir. Methodology SWAT Model Computer simulation models may be costeffective tools for examining nutrient transport within watershed. In past two decades, several computer simulation models, namely ANSWERS (Area Nonpoint Sources Watershed Environmental Response Simulation), SWRRB (Simulator for Water Resources in Rural Basins) and AGNPS (Agriculture Non Point Sources), have been developed to estimate watershed responses to various rainfall events (Young et al., 1989; Spruill et al., 2000). One of the more widely used water quality model is the Soil Water Assessment Tool SWAT (Neitsch et al., 1999), which was development to asses the water quality impacts of agriculture and other land uses for range of watershed scales, including large river basin (Arnold et al., 1998). It operates on daily time step and is designed to predict the impact of management on water, sediment, and agricultural chemical yield. In SWAT, the watershed is divided into multiple subwatersheds, which are then subdivided in to land use characteristics called hydrologic Response Units (HRUs). Flow generation, sediment yield, and non point sources loading from each HRU in subwatershed are summed and resulting load are routed through channel, ponds, or reservoirs to the watershed outlet. Model Set Up Basic input data required to set up a SWAT run are topography, weather, land use, soil, and management data. Topography data were obtained from the BAKOSURTANAL (National Coordinating Agency for Surveys and Mapping) in digital format at scale 1:25,000. Then the SWAT Arc View interface (AVSWAT) was used to develop SWAT input files for the watershed. In this study, Selorejo watershed was divided into four subwatersheds ( Konto upstream, Kwayangan river, Konto downstream, and Penjal river) and were projected to zone 18 of the Universal Transverse Mercator 1983 (UTM- 1983) using the Arc View Extensions of Grid Projector and Projection Utility Wizard, respectively. To improve the delineation accuracy and efficacy, a polygon mask theme, which is slightly larger than Selorejo watershed boundary, was visually created from the projected national hydrology dataset using Arc View. In the watershed delineation dialogue box of the interface, the DEM grid was specified as the projected National elevation dataset, the focusing watershed area option specified as the polygon mask theme and Burn in option (Wang Xixi, and Cui P, 2001) Weather data (daily precipitation and temperature) was colleted from 4 climate station located in or near the watershed. Land 5

6 use, soil and management data were obtained from the Department of Agriculture and Forest with scale 1: Results and Discussion Runoff generated by the AVSWAT2000 is based on the Soil Conservation Services (SCS) runoff equation. The SCS curve number is a functional of a soil s permeability, land use and antecedent soil water condition for dry soil. Outcomes from model simulation from 2000 to 2005 were accurate when compared with the measured data ( R 2 = 0,85). Calibration of SWAT was performed for 2000 while 2001, as shown in Fig 8. First step, SWAT simulation was executed for with land use data 2000 condition. Second; SWAT simulation was executed for with land use data 2005 condition. (See Fig.9) Result of SWAT simulation was divided into tree phases, first in land area, second in stream and finally at reservoir. Nitrogen (mg/l) Mesured Figure 10a. Comparison of annual Nitrogen concentration ( ) and prediction ( ) Nitrogen R2 =0, Measured Figure 10b. Comparison of annual Nitrogen concentration ( ) with R 2 =0,61 Discharge (m3/dt) /14/00 4/14/00 Measured 6/14/00 8/14/00 10/14/00 12/14/00 2/14/01 4/14/01 6/14/01 8/14/01 10/14/01 12/14/01 Phosphorous (mg/l) Mesured Figure 8. Discharge calibration on period Figure 11a. Comparison of annual Phosphorous at period ( ) and prediction ( ) R unoff (mm) Jan Feb Mar Ap mei Jun Jul Aug Sep Oct Nop Des Figure 9 shows the monthly runoff at land area at 2000 compare with 2005 and Phosphorous R 2 =0, Mesured Figure 11b. Comparison of annual Phosphorous concentration ( ) with R 2 =0,78 6

7 Comparison at the year 2000, 2005 and 2010, showed that value of average annual runoff was significant changed Figure 8a and 8b shows the annual nitrogen concentration comparison of measured and simulated ( ) and than predicted of nitrogen at period Result simulation was underestimate with correlation as indicated by R 2 =0,61 Figure 11a. and 11b shows the annual phosphorous concentration comparison of measured and simulated ( ) and than predicted of phosphorus at period Result simulation was underestimate with correlation as indicated by R 2 =0,78 Spahr, N.E., end K.H. Wynn Nitrogen and phosphorous in surface water of the Colorado River Basin. Journal of the American Water resources Association,.33: Young, R.A., C.A. Onstad, D.D Bosh, and W.P Anderson AGNPS. A Nonpointsource pollution model for evaluating agricultural watershed. J. Soil Water Cons, 3.168, 173. Wang Xixi, and Peilian Cui, Support soil conservation practices by identifying critical erosion areas within an American watershed using the GIS-AGNPS model. Conclusion The SWAT model was the first time applied to the Selorejo reservoir Catchment area which is located in Brantas River basin East Java. The model was calibrated for the flow and initial results are presented for the nitrogen and phosphorous loadings in the watershed. In general, the change of land cover in the land would be effected to increase runoff especially for nutrient loading on reservoir. The SWAT model was found to predict flow and nutrient well although at several time was underestimate, and future research is being carried to improve the difference scenario. Reference Arnold, J.G., R. Srinivasan, R.S. Muttiah, and J.R. Williams Large Area Hydrologic Modelling and Assessment. Part I. Model development. J. Am. Water Resource. Assc. 34: Dyad Rahway, Pengkajian Awal Kasus Pencemaran Waduk Karangkates, Malang Jawa Timur, Pusat Penelitian dan Pengembangan Sumber Daya Air, Leone, A., F. Preti, M.N.Ripa, and G. Benigni, (2001), Evaluating of Agricultural Nutrient Diffuse Sources and Related Land Management. Rivista Di Ingegneria Agraria, XXXII (1):20-25 Lone A. & M.N. Ripa, (2002), Land use, Pollutant Nonpoint Sources and Related Modelling for Lakes Management. Lake Vico Experinece, Bolsena Int. Conference, 1-3 October Neitsch, S.L., J.G. Arnold, J.R. Williams (1999) SWAT-Soil and Water assessment Tool- User s Mannual Version