Prospect of Discharge at Daecheong and Yongdam Dam Watershed under Future Greenhouse Gas Scenarios using SWAT Model

In this study, the future expected discharges is analyzed at Daecheong and Yongdam Dam Watershed under Future Greenhouse Gas Scenarios based on RCM with 1 km spatial resolutions from Korea Meteorological Agency(KMA). HadGEM2-AO, which is the climate change prediction model that KMA recently introduced is used for this study. Geum river watershed area is 9,914.013 km2 and there are two dams, one of dam is Daecheong Dam completed in 1980, the other dam is Yongdam Dam completed in 2001. The runoff is simulated using the ArcSWAT model from 1988 to 2010. The simulation is in good agreement with measured data at the Yongdam Dam and Daecheong Dam showing R2 of 92.25% and 95.40% respectively. Using the average discharge from 2001 to 2010 as a baseline, the simulated annual average discharge increased by approximately 47.76% and 36.52% under the RCP4.5 scenario and RCP8.5 scenario respectively for the from 2011 to 2100

Characteristics of Rainfall-Discharge and Water Quality at Limboto Lake, Gorontalo, Indonesia

Problems of high turbidity, sedimentation, water pollution and siltation occur at Limboto Lake, Gorontalo, Indonesia. The objective of this study was to analyze the rainfall-discharge relationship and its implications for water quality conditions. Secchi disk (water transparency), chlorophyll-a (chl-a), and total organic matter (TOM) were measured in May 2012, September 2012 and March 2013 at three sites of the lake (L-1, L-2 and L-3) to observe the impacts on the surrounding catchment. Based on representative stations for rainfall data from 2004 to 2013, monthly averages of rainfall in March-May (166.7 mm) and September (76.4 mm) were used to represent the wet and dry period, respectively. Moreover, sediment traps at these three sites were installed in September 2012. Based on the analysis it is suggested that rainfall magnitude and land use change at the Alopohu River catchment influenced the amount of materials flowing into the lake, degrading the water quality. Specifically, the higher average rainfall in May (184.5 mm) gave a higher average total sediment load (4.41 g/L/day). In addition, water transparency decreased with increasing chl-a. This indicates that the concentrations of sediment and nutrients, reflected by the high amount of chl-a, influenced the water quality conditions

Valve Location Method for Evaluating Drain Efficiency in Water Transmission Pipelines

Water transmission pipelines, which transport bulk water into storage facilities, usually have a tree-type configuration with large dimensions; thus, the breakage of a pipeline may cause a catastrophic service interruption to customers. Although drain efficiency is closely related to the number of washout and control valves and their locations, there is no useful guideline. This paper proposes a valve locating method by introducing numerical analyses to enumerate drainage time and zone. A time integration method, combined with the Newton–Raphson algorithm, is suggested to resolve drainage time, while considering the friction loss in gravitational flow. A drain direction matrix, which shows drain direction and coverage, is derived using a network searching algorithm. Furthermore, a feasible practical approach is presented by introducing a critical horizontal slope, a major washout valve, drainage indices, and control valve embedment. The developed method is first applied to simple pipes to validate the drainage time module. Subsequently, the model is expanded to the CY transmission line, which is one of the BR water supply systems in South Korea currently in operation. The results reveal that three drain valve locations have been neglected, and the addition of control valves guarantees consistent drain time below the operational criteria. Document type: Articl

RESERVOIR INFLOW SIMULATION USING MIKE NAM RAINFALL-RUNOFF MODEL: CASE STUDY OF CAMERON HIGHLANDS

Ringlet Reservoir in Cameron Highlands impounds water mainly from four main rivers namely Sg. Telom, Sg. Habu, Sg. Ringlet and Sg. Bertam. Due to the absence of gauge flow data, MIKE NAM rainfall runoff model was used to simulate inflow for short term and long term prediction. Peak flow is sensitive towards any changes in Umax, TG, CQOF, CKBF, CKIF and CK1,2. All parameters except CK1,2 are sensitive in calculation of total volume. Model was calibrated for the period from 1999 to 2006 and validated for the period from 2010 to 2012 at two streamflow locations. The model is reliable to simulate flow satisfactorily especially during flood events. Model shows good agreement between the simulated and observed flow in terms of low flow, peak flow and total volume. Good calibration results were achieved for all scenarios, with NSE > 0.66, RSR 0.74 and PBIAS (%) < 15%

A sediment discharge computation procedure based on a time-integrated point sample.

A procedure for computing total suspended sediment load using a single point-integrated sample is presented. A power velocity distribution and Laursen's concentration distribution equation (1980) are used: U/U = (x + 1) (y/D)ˣ and C/Cₐ = (a/y)ᶻ where x = 1/4 to 1/7 and z = w/(βκ√(τ₀/ρ); other symbols are as commonly used. The procedure was tested with USGS (1971) field data from the Rio Grande. Using nominal values of β, κ, and w results in estimates of total suspended concentration that agree sufficiently well with depth-integrated measurements corrected for unmeasured load; even better agreement was obtained when site-specific data are used to define the x and z exponents. The difference between total suspended load computed using this procedure (and a single measurement) and conventional computations based on depth-integrated measurements is well within sampling error. For fine sediment (small z value) errors in measurements do not have a large effect on the integrated sediment load. For coarse sediment, however, placement of the sampler, elevation of the bed, and other values must be known with more precision. The typical scatter in suspended sediment load versus discharge plots can be explained by considering possible changes in bed material over time. Laursen's (1958) relationship for total sediment load can be used to evaluate such changes and to calculate bed load. There are major advantages in estimating total suspended load using one time-integrated suspended-sediment point sample. Less field time is required; sampling costs are greatly reduced; and sampling can be more frequent and better timed to measure the changing sediment load. Automatic sampling procedures are more feasible

The comparative sediment processes in channel and overbank

The question posed in this study is why alluvial soil on a floodplain is finer than the bed material of the river that supplied the sediments deposited to form the floodplain. A schematic, simplified river/floodplain system is used in an approximate analysis to find the size distribution of the floodplain soil. It is assumed that the stable limiting condition is a suspended load in the floodplain flow of the same concentration and composition as the sediment load in that portion of the river channel flow above the level of the floodplain. It was found that floodplain soil should be finer than the channel bed material; how much finer depending on the bank height, and to a lesser degree the width of the floodplain

Impacts of Spatial Interpolation Methods on Daily Streamflow Predictions with SWAT

Precipitation is a significant input variable required in hydrological models such as the Soil & Water Assessment Tool (SWAT). The utilization of inaccurate precipitation data can result in the poor representation of the true hydrologic conditions of a catchment. SWAT utilizes the conventional nearest neighbor method in assigning weather parameters for each subbasin; a method inaccurate in representing spatial variations in precipitation over a large area, with sparse network of gauging stations. Therefore, this study aims to improve the spatial variation in precipitation data to improve daily streamflow simulation with SWAT, even pre-model calibration. The daily streamflow based on four interpolation methods, nearest neighbor (default), inverse-distance-weight, radial-basis function, and ordinary kriging, were evaluated to determine which interpolation method is best represents the precipitation at Yongdam watershed. Based on the results of this study, the application of spatial interpolation methods generally improved the performance of SWAT to simulate daily streamflow even pre-model calibration. In addition, no universal method can accurately represent the long-term spatial variation of precipitation at the Yongdam watershed. Instead, it was observed that the optimal selection of interpolation method at the Yongdam watershed is dependent on the long-term climatological conditions of the watershed. It was also observed that each interpolation method was optimal based on certain meteorological conditions at Yongdam watershed: nearest neighbor for cases when the occurrence probability of extreme precipitation is high during wet to moderately wet conditions; radial-basis function for cases when the number of dry days were high, during wet, severely dry, and extremely dry conditions; and ordinary kriging or inverse-weight-distance method for dry to moderately dry conditions. The methodology applied in this study improved the daily streamflow simulations at Yongdam watershed, even pre-model calibration of SWAT

Flood Forecast and Early Warning with High-Resolution Ensemble Rainfall from Numerical Weather Prediction Model

12th International Conference on Hydroinformatics (HIC 2016) - Smart Water for the FutureThis paper investigates the applicability of ensemble forecasts of numerical weather prediction (NWP) model for flood forecasting. In this study, 10 km resolution ensemble rainfalls forecast and their downscaled forecasts of 2 km resolution were used in the hydrologic model as input data for flood forecasting and application of flood early warning. Ensemble data consists of 51 members and 48 hr forecast time. Ensemble outputs are verified spatially whether they can produce suitable rainfall predictions or not during the 2013 Typhoon No. 18, ‘Man-yi’ event. Then flood forecasting driven by ensemble outputs is carried out over the Katusra river basin of the Kinki area, Japan

Geomorphologic Analysis of Small River Basin within the Framework of Fractal Tree

This paper presents the modified framework of geomorphologic analysis based on the concept of fractal tree. Especially, it is intended to provide hydrologic practitioners with the information on the fractal property of small river basins. To this end, the complete drainage path network is applied to a growth process of a fractal tree for the basin of interest by connecting a channel network to overland drainage pathways. The growth process of a fractal tree would occur only within the limited region possessing channel flow properties in a natural river basin. The exponent of the intra basin type of Hack&rsquo;s law could show a variable trend in small river basins mainly due to anisotropic property of the catchment planform. The bifurcation process of a drainage path network might be more sensitive to the growth step of the fractal tree than the meandering process of drainage path segment. The fractal dimension from the sinuosity of a channel segment is relatively stable compared to the one from the bifurcation process of the network, so that the geomorphologic features of a small river basin can be characterized by the anisotropic property of catchment planform as well as the bifurcation property of drainage path network with the growth of the fractal tree

Ecological Evaluation of Reach Scale Channel Configuration for Watershed Management

12th International Conference on Hydroinformatics (HIC 2016) - Smart Water for the FutureReach-scale channel configuration (RSCC) such as braided, meandering, wandering or straight channels could be use as target condition in river management of watershed scale. This study aims at revealing relations between hydro-geomorphological RSCC and ecological diversity, and suggests one methods in evaluation of river condition using only aerial photo. The investigation was conducted on the Kizu River located in central Japan, where riverbed degradation and vegetation expansion proceeded after dam construction and sand excavation over a 65-year period. In order to evaluate RSCC, we classified type of aquatic habitat structure as one of the ecological parameters and analysed relations between RSCC and habitat structures/diversity. According to relations RSCC and habitat structures, wandering channel types tended to have higher potential of lentic and lotic habitat quantity and quality than single or braided channel