Dam Construction Impacts on Stream Flow and Nutrient Transport in Kase River Basin

Transcription

1 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 12 No: 03 1 Dam Construction Impacts on Stream Flow and Nutrient Transport in Kase River Basin Cindy SUPIT 1, 2 and Koichiro OHGUSHI 1 1 Department of Civil Engineering and Architecture, Faculty of Science and Engineering, Saga University. 1 Honjo, Saga , Japan; supit.cindy@yahoo.com and ohgushik@cc.saga-u.ac.jp 2 Department of Civil Engineering,Sam Ratulangi University,Kampus Unsrat Bahu,Manado 95111,Indonesia Abstract Kase River Basin in Saga Prefecture is one of the most important rice production bases in Kyushu Island, Japan. A new multi-purpose Kase River Dam has been constructed just downstream of another old agricultural dam, Hokuzan dam in Saga Prefecture, Japan. Forest and agricultural areas have been changed from artificial coniferous forest and rice field to water area. This study is to evaluate the future potential impacts of dam construction on stream nutrient transport for a km 2 mountains dam watershed in Kase River basin using SWAT (Soil and Water Assessment Tool) model. The SWAT model was calibrated and validated using 2 years ( ) daily stream flow data with the coefficient correlation = 0.86 and Nash-Sutcliffe index = To describe effects on hydrological process from operating dams, various scenarios were examined, using the calibrated model. The set of scenarios tested the impact of the existence or nonexistence of dam reservoirs in the watersheds. The result of this study indicates that excessive dams in Kase River basin has changed dramatically the stream flow regimes by a decrease of monthly stream flow rates in the watershed up to 29.3% from the disappeared dam scenario. Impoundments have less efficient on stream nutrient transport, based on results at Furuyu point. The future change of monthly stream and nutrient transport gave us the clue to be suggested for future adjustment of dam operation rule to optimize water resources and pollution control in Kase River basin. exchange of water in dam, and due to water impounding by the dam so water quality in downstream might be changed (Horne et al. 2004; Betnarek et al. 2001; Berkamp, et al. 2008).. To study the impact of water projects such as dam construction on environmental water quality and quantity is important for river basin management and environmental protection, such as impact of dam to hydrological process ( Nislow et al. 2002; Hayes et al. 1998) and water quality ( Somura et al. 2009), The objective of this study is to illustrate the impact of dam construction on stream flow and nutrient loading from Kase River Basin. These estimates give a potential strategy to manage future downstream nutrient and water resources in Kase River basin. Index Terms Dam construction, Stream flow, Nutrient transport, Kase River Basin I. INTRODUCTION Japan is the first nation in the Asian Monsoon zone to achieve modern industrialization and it did this in the relatively short period of about 100 years, beginning in the late nineteenth century. Dams in Japan supported social and economic development that preceded modernization and have been viewed as symbols of modernization and of social vitality that utilizes nature. However since the 1980s, dam projects have concerned criticism from the community, because their substantial impacts on the social order and the natural environment are becoming obvious(jcold, 2009). There are some impacts such as impacts on water quality and quantity; alteration of runoff and evaporation processes, risk of increasing diffuse inputs to rivers due to increase in erosion and landslides, higher potential of eutrophication because of limited Fig. 1. Watershed delineation in the study area

2 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 12 No: 03 2 A. Methods II. METHODS AND DATA SOURCE SWAT is a river basin or watershed, scale model developed to predict the impact of land management practices on water, sediment, and agriculture chemical yields in large, complex watersheds with varying soil, land use, and management conditions over long periods of time (Arnold et.all 1998). ArcSWAT 2009, a third-party software extension to ArcGIS, is used as an interface between ArcGIS and the SWAT model. Spatial data (DEM, soil and land use) is used in the preprocessing phase and fed into the SWAT model through the interface. Climate, precipitation, stream flow and water quality data were sourced and prepared according to SWAT input requirements. This model was chosen because it is computationally efficient and enables to study long impact (Neitsch, 2002). The hydrologic cycle of the SWAT model is based on the water balance equation, which considers the unsaturated zone and shallow aquifer above the impermeable layer as a unit. The SWAT water balance equation is B. Data source Topographic data ArcSWAT 2009 uses DEM data to automatically delineate the watershed into several hydrological connected sub watersheds. In this paper, DEM data with resolution of 50 meter were used. The DEM was taken from Nippon-III of digital map; the watershed was then divided into 23 sub watersheds in the SWAT model. Fig.1 and Fig.2 show watershed delineation in the study area and DEM data which used for this study respectively. SW t = SW + ( R t Q E w Q 0 day surf a seep gw i= 1 ) (1) where SW t is the final soil water content, SW 0 is the initial soil water content, t is the time (days), R day is the amount of precipitation on day i, Q surf is the amount of surface runoff on day i, E a is the amount of evapotranspiration on day i, w seep is the amount of percolation and bypass flow exiting the soil profile bottom on day i, and Q gw is the amount of return flow on day i. The SWAT model uses the SCS curve number procedure to calculate the runoff volume under different soil types and land uses. The SCS curve number equation is Q surf ( R = ( R day day I I a a ) 2 + S) (2) Fig. 2. DEM data for the study area where Q surf is the accumulated runoff or rainfall excess (mm); R day is the rainfall depth for the day (mm); Ia is the initial abstractions, which includes surface storage, interception, and infiltration prior to runoff (mm); and S is the retention parameter (mm). The retention parameter varies spatially due to changes in soil, land use, management, and slope and temporally due to changes in soil water content. The retention parameter is defined as S = CN (3) where CN is the curve number for the day. Land use data Kase River Basin has wide variety of land use while MLIT (Ministry of Land, Infrastructure and Transportation) Japan due to National Comprehensive Water Resources Plans was added a new multi-purpose dam in this area in order to supply water needed especially for agriculture and water supply in Saga Prefecture. Land use data of 2007 were applied and 13 land use types in the study area were reclassified using SWAT land use classes. The land use classes were converted from original land use classes to SWAT classes and defined using a look up table. Table 1 shows the land uses conversion from original land uses classes to SWAT classes.

3 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 12 No: 03 3 TABLE 1 LAND USE CONVERSION FROM ORIGINAL LAND USE CLASSES TO SWAT CLASSES Original land use classes Corresponding SWAT classes SWAT Code Park green space Commercial UCOM River, Lake, Pond Water WATR Road and Railway Transportation UTRN Resident Residential URBN Communal Institutional UINS facilities Factory, power Industrial UIDU plant Rice field Rice RICE Orchard Orchard ORCD Natural coniferous Forest evergreen FRSE forest Artificial Forest decidduous FRSD coniferous forest Moorland Pasture PAST Cut over land Summer pasture SPAS Collapse ground r Wetlands non forested WETN Observatory were applied in order to calculate the potential evapotranspiration (PET) using Penman-Monteith`s method. Hydrological data Daily observed discharge data were taken by MLIT ( ) for the analysis. Stream flow rate were processed from hourly to daily average value and will processed for calibrating the SWAT model. Prior to calibration, 4 most sensitive parameters: CN2, GWQMN, Alpha_BF, and Sol_AWC, were selected and adjusted manually based on previous SWAT research in Japan mountains area. Available data from January to December, 2008 were used for the calibration and the daily stream flows in 2009 at the Furuyu station located just in the downstream of the new dam were applied for validation. Fig.4 shows comparison on simulated and observed discharge with the coefficient correlation = 0.86 and Nash-Sutcliffe index = Soil data Detailed soil map was clipped from National Land Survey Division, Land and Water Bureau of MLIT`s website and was used as the GIS input data for the model simulation. Land use and soil data in WGS 1984 UTM Zone 52N projected were loaded into the ArcSWAT 2009 to determine the area and hydrologic parameters of each land-soil category simulated within each sub basin. Fig. 4. Comparison on simulated and observed discharge in Furuyu outlet during Fig. 3. Spatial data soil map Weather data SWAT required climate data to provide the moisture and energy inputs that control the water balance and determine the relative importance of the different component of the hydrology cycle. Hourly observed weather data (temperature, humidity, solar radiation) from Saga Meteorological Dam data According on the available data and the necessary inputs of the SWAT, the following characteristic indicators of the dam were set up: the surface area of reservoir when filled to the emergency spillway, surface area of reservoir when filled to the principal spillway, volume of water held in reservoir when filled to the emergency spillway, and volume of water held in the reservoir when filled to the principal spillway.. Water quality data Data on the nutrient parameters before and after dam impoundment were observed by MLIT. In this study, the data from November 2008-March 2011 are used. The period of water quality data before impoundment from November 2008 to October 2010 represent the time when the water had not exist in the reservoir yet, and due to available data, Furuyu point represents the point sources to downstream riverine nutrient.

4 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 12 No: 03 4 TABLE 2 AVERAGE MONTHLY STREAM FLOW RATES AT FURUYU UNDER THE SCENARIOS Fig. 6. TN concentration in Furuyu outlet ( ) Month Hokuzan and Kase dam Q (m 3 /s) Hokuzan dam only January February March April May June July August September October November December No dam Fig. 5. Change in peak stream flow with respect to the scenarios comparison between downstream area and all watersheds III. RESULT The developed model was tried to run using model input and physical parameters as described above. Unsurprisingly, the existence of dams resulted in major reductions in stream flow rate in the watershed. The outcome also showed that the presence of Hokuzan dam and Kase River dam in the watershed caused larger reductions in stream flow than the only Hokuzan dam did. These dams seem to result in decrease of monthly discharge by up to 29.3% from the disappeared dam scenario. The decrease of stream discharge from this adjustment may be recognized to the verity that those dams divert water to off stream uses such as irrigation and urban uses (multi-purpose), especially out of basin diversions, will reduce the total downstream flow (Collier et al, 1995). Excessive dams and floodgate operations have change dramatically the flow regimes and shift peaking time (J. Xia, et al. 2005). Fig. 7. TP concentration in Furuyu outlet ( ) These effects on decrease of stream flow by increased number of dams in the watershed are mainly strong in the wet period from June to July, because precipitation is plentiful in the wet period and temperatures are high enough to support high evaporation. Therefore, as shown in Table 2, the stream flow rates decreased significantly for the period. Decreases in discharge also occur in the periods after the wet period. The quite lower decrease in discharge in the August September period is resulting from hot temperatures in those months. From Fig. 5, we have found moderately large differences in watershed peak flow between the conditions while changes of peak flow in Kanjimbashi and Furuyu are large among the scenarios. A large decrease of Furuyu and Kanjimbashi peak flow indicate that the effect of dam construction is seen significantly in the lowering peak flow at downstream of watershed. Peak flow rates in all watershed decreased by 12.31% when the Hokuzam dam and Kase River dam were added from the current condition. In Furuyu, a change of annual

5 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 12 No: 03 5 peak flow rate decreased by 23.45% due to scenario 2. Dams impoundments have less efficient effect on downstream nutrient transport (Fig.6 and Fig.7). The presence of the new Kase dam results in decreasing of total nitrogen in November, January and March at Furuyu point, just downstream after the Kase River dam. The Furuyu`s TN showed a decrease tendency up to 7.85%, but the TP showed average 18.45% decrease in November, February, March, and 29.2 % increase in December and January. IV. CONCLUSIONS Excessive dams in Kase River basin has changed dramatically the stream flow regimes The impoundment of the new Kase dam has less efficient in decreasing of total nitrogen and total phosphorus at downstream. The SWAT model successfully passed the scenarios exercises considering stream flow rates output. Model setup and water quality calibration works are already in progress as a next step for analysis. Some issues still need to be addressed for better assessment of dam impacts. Coupling the SWAT model and a hydrodynamics model inside the reservoir should be done in the next step. [12] Somura. H, Hoffman.D, Arnold. J, Application of the SWAT Model to the Hii River Basin, Shimane Prefecture, Japan, 4th International SWAT Conference.2009 [13] Supit C, Ohgushi K, Prediction of dam construction impacts on annual and peak flow rates in Kase River Basin. Annual Journal of Hydraulic Engineering, JSCE, Vol.56, 2012 [14] Xia J, Wang ZG, et al. An integrated assessment method of water quality & quantity applied to evaluation of available water resources. Journal of Natural Resources, 2005 [15] Yang T, Zhang Q, Chen YD, Tao X, Xu CY, Chen X. A spatial assessment of hydrologic alteration caused by dam construction in the middle and lower Yellow River, China. Hydrol Process 22(18): ACKNOWLEDGMENT The authors would like to acknowledge MLIT for data and their cooperation in the project, SWAT community for model setting discussions and Indonesian government for supporting the study. REFERENCES [1] Arnold, J.G., Srinivasan, R., Muttiah, R.S., Williams, J.R., Large area hydrologic modeling and assessment Part 1: model development. Journal of the American Water Resources Association 34 (1), ) 1998 [2] Bartholow JM, Campbell SG, Flug M. Predicting the thermal effects of dam removal on the Klamath River [J]. Environmental Management, [3] Berkamp G, McCartney M, Dugan P, et al. Dams, ecosystem functions and environmental restoration, WCD thematic review environmental issues II.1. Cape Town: the World Commission on Dams, [4] Bednarek AT. Undamming rivers: a review of the ecological impacts of dam removal. Environmental Management, 2001 [5] Hayes, D. F.,Labadie, J. W. & Sanders,T. G..Enhancing water quality in hydropower system operations. Water Resources Research, 1998 [6] Horne BD, Rutherford ES, Wehrly KE. Simulating effects of hydro-dam alteration on thermal regime and wild steelhead recruitment in a stable-flow Lake Michigan tributary. River Research and Applications, 20 (2): [7] Japan Commission on Large Dams. Dams in Japan: Past, Present and Future. The Nederlands: CRC Press, [8] Nash, J.E., Sutcliffe, J.V., River flow forecasting through conceptual models: Part 1 a discussion of principles. Journal of Hydrology 10 (3), [9] National Land Survey Division, Land and Water Bureau of Ministry of Land, Infrastructure, Transport and Tourism (2007), [10] Neitsch, S.L., Arnold, J.G., Kiniry, J.R., Williams, J.R. King, K.W. Soil and Water Assessment Tool Theoretical Documentation: Version Agricultural Research Service, Temple, Texas, [11] Nislow KH, Magilligan FJ, Fassnacht H, Bechtel D, Ruesink A. Effects of dam impoundment on the flood regime of natural floodplain communities in the upper Connecticut river. J Am Water Resour Assoc 38(6):