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The impact of climate change on the quantity and quality of the surface runoff of the three reservoir upper watersheds: Dokgray, Nong Pla-Lai and Klong-Yai

Assit. Prof. Booncherd  Nu-Im


Assit. Prof. Booncherd Nu-Im
Ph.D. Candidate in Environmental Science,
Faculty of Science, Burapha University, Thailand
E-mail: [email protected]

Abstract

This research aimed to assess the quantity and quality of the surface runoff affected by climate change in the watershed areas in the eastern part of Thailand. The three reservoirs studied were: Dokgray, Nong Pla-Lai and Klong-Yai. The researcher employed many methods such as Comformal Cubic Atmospheric Model (CCAM), Soil and Water Assessment Tool (SWAT), and Digital Elevation Model (DEM). It was found that the rain quantity increased. The delineation of the protected environment areas and the land use in 2003 in case of the carbon dioxide increased from the present level 1.5 times (540) and two times (720 ppm) was different significantly between the underground water quantity and the total water quantity. Also, the delineation of the protected environment areas, which made land use of the water resources, forest, industry, and community increased, whereas the agricultural area decreased, causing the reduction of the underground water quantity and total water quantity. For the surface water quality, it was found that they were different significantly. The land use as the delineation of the protected environment area had effect on the surface runoff quality in the future. Keyword: climate change, SWAT model, hydrology

Introduction

There are main water reservoirs in the eastern coast of Thailand, Dokgray, Nong Pla-Lai and Klong Yai. Raw water from these reservoirs has been used for consumption, industry and agriculture. The upper watershed areas of these three reservoirs have been specified as the middle area of the master plan of the land use and community of the eastern coastal areas stage 2, which still remains as the semi-agricultural countryside area. The special characteristics of those areas are that there are potentials for setting up new cities. There are many industrial estates in the southern area near the port of Laemchabang, including the convenient transportation network that enables the area to have the potential of the industrial investment. However, since these areas are the upper watershed areas and are nearby the preservation areas, there is environmental sensitivity on the occurring changes. There will be the expansion of the development areas for the industry and the city community in the future, which will have impact on the quantity and quality of the surface runoff. This study is concerned with future land use that has the government policy for the delineation of the protected environmental areas and the climate changes from the CCAM (The Conformal Cubic Atmospheric Model) in case of the carbon dioxide increased from present level 1.5 times (540 ppm) during the years 2024 to 2033 and two times (720 ppm) during 2052 to 2061.

Objectives of the research

To study the impact of climate change on the quantity and quality of the ground surface water in the upper water area, namely the Dokgray Reservoir, the Nong Pla-Lai Reservoir and the Klong Yai Reservoir.

Literature Reviews

Land use has important roles which induce different hydrologic watershed systems for each area (Heuvelmans, Muys, & Feyen, 2005). Land use has effects on the vanished quantity of the surface water due to the confinement on surface, evaporation emission and permeability. The absolute forest area will cause less surface flow but will induce more vanished rain due to confinement, more permeability and more water restraining around the plant roots. On the other hand, in the city community area mainly covering with the impervious area, there will be much quantity of the surface flow and rapid flow rate. Tan, Melesse, and Yeh (2000) has applied remote sensor images and the geologic information technology to the estimation of the runoff quantity by using the methodology of SCS-CN Curve Number. They found that during 1990, 1995 and 2000, land use in the town area increased, whereas agricultural areas reduced causing the incline of the runoff quantity. Moreover, the increase of the forest areas reduced of the flow rate and the surface water quantity (Weber, Fohrer, & Moller, 2001), but the baseflow increased relatively (Fohrer, Eckhardt, Haverkamp, & Frede, 2001). The increasing land use change for the agriculture influence the raised quantity of the surface water, including the increased transmission of the sediments and nutrients into water resources (Lenhart, Fohrer, & Frede, 2003). Whereas, the watershed area that mainly has the land use for the agriculture and for the pasture land or empty land has the small impact on the surface water quantity (Huisman, Breuer, & Frede, 2004). However, the important thing is to have the regulation for the soil and water preservation in order to provide the watershed management and to preserve the water balance as well (Behara & Panda, 2005) Climate changes induce the change of the natural balance and have the impact on the global resources and the global food production. The increased heat would cause the variation on the temperature and climate, drought and heavy rain causing more floods. In Thailand there is a study of the climate change, which found that the trend of the temperature is inclined approximately 2.5 to 4 degree Celsius. Furthermore, Norman, Bery, Brown, Lzauralde and Thomson (2003) studied the impact of the climate change on agriculture by using the General Circulation Model (GCM: Had CM2) to study the climate change during two periods, in 2030 and 2095. The study has applied the SWAT model on the study of the hydrologic change and found that the water balance increased 35 % in 2003 and will increase 38% in 2095 induced by the increase of the carbon dioxide from 365 ppm to 560 ppm. The raised rain would cause the increase of the surface water quantity, which affected the transmission of the nutrients and sediment within the watershed area (Boorman, 2003) Neitsch, Arnold, Kiniry, Williams and King (2002) have generated the Soil and Water Assessment Tool (SWAT), which is copyright-free and can be applied to several studies. The SWAT has the ability to simulate the complicated models in terms of hydrology, DDT, the nutrient chain, the erosion and displacement of the sediment. The SWAT has been developed in the study of the quantitative effect of the management of large watershed area or large rivers. This tool will consume mainly the physical data and will enable the study of the effect in long term.

Research Methodology

Study Areas

The studied areas are the watershed areas of three reservoirs, namely the Dokgray, the Nong Pla-Lai and the Klong Yai. The location of the studies area was between Chonburi Province and Rayong Province.(Fig. 1)

Data Sources and Data Collection

The data was obtained from sources of many Thai government’s units, digital data of remote sensor images, map and the land use data during years 2003, the contour map data, soil group map data at the scale 1: 50,000, water route data at the scale 1: 50,000, climate data composed of the daily rain data, the maximum and minimum daily temperatures since 1989 to 2003, the runoff measurement data since 1989 to 2003, the map of the environmental preservation area at the watershed area of the Nong Pla-Lai, Dokgray and Klong-Yai reservoirs, the climate change data retrieved from the Conformal Cubic Atmospheric Model (CCAM) in case of the carbon dioxide level increase from the present 1.5 times (540 ppm) during years 2024 to 2033 and increased twice (720 ppm) during 2052 to 2061, retrieved data from the Network Center for the Analysis, Research and Training of the Global Change at the South East Asia region, Chulalongkorn University, water quality data from the analysis report of the industrial park about the environmental impact on the studied areas, and Field data, which examined the land use and the coordination of the involved in local administration offices.

Data Analysis

  1. The data on land use from the DEM using the SWAT model and the Arc view program, enabling the collection of the coordinated data in the area and the level within each grid cell that has the same size in order to analyze the topography surface of the data of each grid cell that continuously jointed together as the same panel.
  2. The SWAT model was employed to get the soil data and characteristic in Thailand.
  3. Data from the CCAM was to analyze the atmospheric condition in three main cases: firstly, the carbon dioxide in normal condition during years 1980 to 1989 (350 ppm), secondly in case of the increase of the carbon dioxide level 1.5 times compare to present level (540 ppm) during years 2024 to 2033, and finally two times of the carbon dioxide level which will occur during years 2052 to 2061.
  4. The runoff quantity was determined by using the SWAT model in conjunction with the Arc view program to assist the analysis.


Fig. 1 The study areas

The impact of climate change on the quantity and quality of the surface runoff of the three reservoir upper watersheds: Dokgray, Nong Pla-Lai and Klong-Yai

Results and Discussion

The Delineation for Sub-watershed Area

The delineation for sub-watershed area was conducted by using the automated watershed delineation tool under SWAT/GIS Interface by using the DEM map, grid size of 50x 50 m., to evaluate the threshold area, which was approximately 200 square kilometer. The watershed of the Dokgray Reservoir has the water reserved area at 321.71 square kilometers. The watershed of the Nong Pla-Lai Reservoir has the area of 410.93 square kilometers. The watershed of the Klong Yai Reservoir has the area 322.54 square kilometers. All the reservoirs cover some parts of both Chonburi and Rayong, Besides, the rainfall analysis in the three reservoirs above found that there was much rain in the watershed area of the Dokgray Reservoir, average quantity at 1,400 millimetre, followed by the watershed of the Nong Pla-Lai and Klong Yai at 1,300 millimetre.

The Model Calibration

1. Calibration areas Data was collected from the water measurement station, used for the calibration in the studied areas and covers the data during 1989 to 2003. The data above retrieved from station named Z15 located in the watershed area of the Klong Yai Reservoir. The calibration was done with the Web-Based Hydrograph Analysis Tool on the flow quantity analysis of the water from the runoff measurement station and from the SWAT model. 2. The calibration result. The surface runoff quantity has the decision coefficient at 0.51 and the efficiency coefficient at 0.34, whereas the baseflow has the decision coefficient at 0.52 and the efficiency coefficient at 0.40. And the total water quantity has the decision coefficient at 0.61 and the efficiency coefficient at 0.55 (Table 1). Therefore, the model calibration has the acceptable statistics value on the data analysis of the surface flow, baseflow and the total water quantity. The data from the SWAT model can be efficiently applied to studied area within the watersheds of the Dokgray, the Nong Pla-Lai and the Klong Yai reservoirs.

Table 1. The decision coefficient, efficiency coefficient and the regression equation.

Water flow quantity Decision coefficient Efficiency coefficient Regression equation
Surface water 0.51 0.34 8.47+1.51X
Baseflow 0.52 0.40 -15.5+0.97X
Total water quantity 0.61 0.55 -31.75+1.48X

Remark: X represented the analysis value gained from the model.

The Impact of the Climate Change on the Quantity and Quality of the Surface Runoff

Climate change has impact on the quantity and quality of the surface runoff. The CCAM data, in case of the carbon dioxide increased 1.5 times (540 ppm) compared to the present level during years 2024 to 2033 and two times (720 ppm) occurred during 2052 to 2061, revealed that the rain quantity in the upper watershed of the three reservoir, Dokgray, Nong Pla-Lai, and Klong Yai has the significant difference. For the two-time increase (720 ppm), there is the average rain quantity at 1,105 millimeter, more than the case of 1.5 times (540 ppm), which has the average rain quantity at 1,069.34 millimeter. The increase of the carbon dioxide at 1.5 times (540 ppm) and two times (720 ppm) has no effect on the hydrologic conditions such as the flow out rate, the surface runoff quantity, the baseflow quantity and the total quantity of the water. The planning for the land use as the allocation of the environment protected area and the land use in 2003 in case of the carbon dioxide increased 1.5 times (540 ppm) and two times (720 ppm) compared to the present amount showed that the Dokgray Reservoir watershed has different quantity of the surface runoff, while the Nong Pla-Lai reservoir watershed has the different flow rate, and the Klong Yai reservoir has the different flow rate, the quantity of the surface runoff, and the baseflow. The allocation of the environment protected area allowed the increasing land use for the water resources, forestry, industry and community. In contrast, the agricultural areas were reduced as the regulation that will affect the hydrologic condition, causing the reduction of the baseflow quantity and the total water quantity.

The surface runoff quality consisted of nitrogen in the organic form, phosphorus in the organic form, ammonia nitrite, nitrite that passed through the area. From the format of the land use as the allocation of the environment protected area and the land use in 2003 in case of the carbon dioxide raised 1.5 times (540 ppm) and two times (720 ppm) from the present level, it was found that within the area of the Dokgray reservoir watershed the quantity of nitrite and the oxygen dissolved into water has some differences. The Nong Pla-Lai reservoir watershed has different ammonia quantity, nitrate and the oxygen dissolved into the water, whereas the Klong Yai reservoir watershed has the differences of the nitrogen in the organic form, the quantity of the phosphorus in the organic form, the ammonia quantity and the quantity of the oxygen dissolved into the water. The environment protected area induced the nutrient corrosion into the water resources rather than the land use format in 2003, which showed that the allocation according to the regulation of the environment protected area would cause the effect on the surface runoff quality.

The following are suggestions for land use planning from the land use analysis in 2003 and the allocation of the environment protected areas in to be in accordance with the climate change in the future.

  1. The area of the Dokgray, the Nong Pla-Lai and the Klong Yai watersheds must have the control of the community and industry expansions. Forest should be planted in the upper watershed areas in order to slow down the runoff flow and to increase the baseflow quantity.
  2. The land use for agriculture is needed for the soil and water preservation. Therefore, the preservation will enable the soil to retain the moisture content. Also, there must be the plantation adjustment to match the climate changes.
  3. Climate changes reduce annual rainfall, but the water demands of the community and industry increased. These demands would reflect the water shortage in the future. Therefore, there must be a plan for the integral water supply management.

Conclusion

Climate change has impact on the quantity and quality of the surface runoff. When the carbon dioxide increased, rain increase as well. Increasing of carbon dioxide has no effect on the hydrologic conditions. Different watershed has different organic forms. The regulation of the environment protected area would cause the effect on the surface runoff quality. The allocation of the environment protected area allowed the increasing land use for the water resources, forestry, industry and community. In contrast, the agricultural areas were reduced. To improve the condition of runoff quality, the control of the community and industry expansion that would obstruct the water ways is suggested, and expanding forest area is encouraged to prevent water shortage in the future.

References

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Boorman, D. B. (2003, October). Climate, hydrochemistry and economics of surface- water systems (CHESS): Adding a European dimension to the catchment modelling experience developed under LOIS. The Science of the Total Environment, 314-316, 411-437. Retrieved October 2005, from ScienceDirect database.

Fohrer, N., Eckhardl, K., Haverkamp, S., & Fred, H.G. (2001). Applying the SWAT model as a decision support tool for land use concepts in peripheral regions in Germany. Retrieved November 10, 2003, from veroeffentlichungen.html

Grizzetti, B., Bouraoui, F., Granlund, K., Rekolainen, S., & Bidoglio, G. (2003). Modeling diffuse emission and retention of nutrients in the Vantaanjoki watershed (Finland) using the SWAT model. Retrieved February 20, 2004, from https://ceprofs.tamu.edu/folivera/ TxAgGIS/Spring2004/MiAeHa/html/ref.htm.

Heuvelmans, G., Muys, B., & Feyen, J. (2005, September). Regionalisation of the parameters of a hydrological model: Comparison of linear regression models with artificial neural nets. Journal of Hydrology. Retrieved October 2005, from ScienceDirectdatabase.

Huisman, J.A., Breuer, L., & Frede, H.G. (2004). Sensitivity of simulated hydrological fluxes towards changes in soil properties in response to land use change. Physics and Chemistry of the Earth, Parts A/B/C, 29(11-12), 749-758. Retrieved October 2005, from ScienceDirect database.

Lenhart, T., Fohrer, N., & Frede, H. G. (2003). Effects of land use changes on the nutrient balance in mesoscale catchments. Physics and Chemistry of the Earth, Parts A/B/C, 28(33-36), 1301-1309. Retrieved October 2005, from ScienceDirect database.

Neitsch, S.L., Arnold, J.G., Kining, J.R., Srinivasan, R., & Williams, J.R. (2002). Soil and water assessment toll user’s manual version 2000. Retrieved August 7, 2003, from .

Norman, J., Bery, R., Brown, R.A., Lzauralde, R.C., & Thomson, A.M. (2003). Integrated assessment of Hadleg Centre (Had CM2) climate change projections on agricultural productivity and irrigation water supply in the conterminous United States I. climate change scenarios and impacts on irrigation water supply simulated with the HUMUS mode. Retrived April 5, 2004, from

Tan, C.H., Melesse, A.M., & Yeh, S.S. (2000). Remote sensing and geographic information system in runoff coefficient estimation in China Taipei. Retrieved March 2, 2004, from .

Weber, A., Fohrer, N., & Moller, D. (2001). Long-term land use changes in a mesoscale watershed due to socio-economic factors – effects on landscape structures and functions. Ecological Modelling, 140(1-2), 125-140. Retrieved October 2005, from ScienceDirect database.