• Economic and Environmental Geology
• /
• v.57 no.2
• /
• pp.107-117
• /
• 2024

The objective of this study is to estimate riverbed fluctuations and the volume of aggregate extraction attributable to climate change. Rainfall-runoff modeling, utilizing the SWAT model based on climate change scenarios, as well as long-term riverbed fluctuation modeling, employing the HEC-RAS model, were conducted for the Nonsan River basin. The analysis of rainfall-runoff and sediment transport under the SSP5-8.5 scenario for the early part of the future indicates that differences in annual precipitation may exceed 600 mm, resulting in a corresponding variation in the basin's sediment discharge by more than 30,000 tons per year. Additionally, long-term riverbed fluctuation modeling of the lower reaches of the Nonsan Stream has identified a potential aggregate extraction area. It is estimated that aggregate extraction could be feasible within a 2.455 km stretch upstream, approximately 4.6 to 6.9 km from the confluence with the Geum River. These findings suggest that the risk of climate crises, such as extreme rainfall or droughts, could increase due to abnormal weather conditions, and the increase in variability could affect long-term aggregate extraction. Therefore, it is considered important to take into account the impact of climate change in future long-term aggregate extraction planning and policy formulation.

• Journal of Korean Society on Water Environment
• /
• v.25 no.6
• /
• pp.821-831
• /
• 2009

The study was aimed to assess the expected impact of climate change on the water cycle and soil losses in Daecheong Reservoir watershed, Korea using the Soil and Water Assessment Tool (SWAT) that was validated for the watershed in a previous study. Future climate data including precipitation, temperature and humidity generated by introducing a regional climate model (Mesoscale Model Version 5, MM5) to dynamically downscale global circulation model (European Centre Hamburg Model Version 4, ECHAM4) were used to simulate the hydrological responses and soil erosion processes in the future 100 years (2001~2100) under the Special Report on Emissions Scenario (SRES) A1B. The results indicated that the climate change may increase in the amount of surface runoff and thereby sediment load to the reservoir. Spatially, the impact was relatively more significant in the subbasin Bocheongcheon because of its lower occupation rate of forest land compared to other subbasins. Seasonally, the increase of surface runoff and soil losses was more significant during late summer and fall season when both flood control and turbidity flow control are necessary for the reservoir and downstream. The occurrence of extreme turbidity flow events during these period is more vulnerable to reservoir operation because the suspended solids that remained water column can be resuspended by vertical mixing during winter turnover period. The study results provide useful information for the development of adaptive management strategy for the reservoir to cope with the expected impact of future climate change.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.62 no.4
• /
• pp.13-22
• /
• 2020

The Doam Lake watershed has a significant impact on the downstream water system due to nutrients and sediment outflow during rainfall caused by steep slopes, soil losses, and fertilization. These non-point sources are unclear in the discharge area and are affected by land use patterns, soil characteristics, and topographical features of the watershed. Therefore, this study conducted rainfall monitoring from July to October 2019 in Songcheon upstream of the Doam Lake watershed, one of the non-point pollution source management areas. Then, after analyzing rainfall runoff, Event Mean Concentration (EMC) and Mass First Flush ratio (MFFn) were calculated to compare and analyze the characteristics of rainfall and the non-point pollutant discharge. As a result of the analysis, it showed various non-point pollutant emission characteristics for each rainfall event. In addition, the concentration of EMC and the MFFn were affected by the average rainfall intensity and the maximum rainfall intensity, and were not significantly affected by the number of antecedent drying days. In the future, it is expected that effective non-point source reduction measures and management measures according to rainfall intensity through continuous monitoring and analysis will be needed.

• Environmental Engineering Research
• /
• v.11 no.4
• /
• pp.194-200
• /
• 2006

Recently, the population growth, industrial and agricultural development are rapidly undergoing in the Lower Rio Grande Valley (LRGV) in Texas. The Lower Rio Grande Valley (LRGV) composed of the 4 counties and three of them are interesting for Non-point and point source pollutant modeling: Starr, Cameron, and Hidalgo. Especially, the LRGV is an intensively irrigation region, and Texas A&M University Agriculture Program and the New Mexico State University College of Agriculture applied irrigation district program, projects in GIS and Hydrology based agricultural water management systems and assessment of prioritized protecting stream network, water quality and rehabilitation based on water saving potential in Rio Grande River. In the LRGV region, where point and non-point sources of pollution may be a big concern, because increasing fertilizers and pesticides use and population cause. This project objective seeks to determine the accumulation of non-point and point source and discuss the main impacts of agriculture and environmental concern with water quality related to pesticides, fertilizer, and nutrients within LRGV region. The GIS technique is widely used and developed for the assessment of non-point source pollution in LRGV region. This project shows the losses in $kg/km^2/yr$ of BOD (Biological Oxygen Demand), TN (total Nitrogen) and TP (total phosphorus) in the runoff from the surface of LRGV. Especially, farmers in Cameron County consume a lot of fertilizer and pesticide to improve crop yield net profit. Then, this region can be created as larger nonpoint source area for nutrients and the intensity of runoff by excess irrigation water. And many sediment and used irrigation water with including high nutrients can be discharged into Rio Grade River.

• Journal of Korean Society on Water Environment
• /
• v.39 no.1
• /
• pp.38-45
• /
• 2023

In this study, the removal efficiency of road sweeping and sand filter facility for removing total suspended solid (TSS) as nonpoint source pollution from expressway was evaluated for the last 10 years (2012~2021) using ROADMOD. ROADMOD is a screening level model and was calibrated for runoff rate and TSS loading both at the inlet, which is the loading from the drainage area, and the outlet, from the sand filter facility. The drainage area is 715 m² and the dimensions of sand filter facility are 1.5 m (wide) × 3.8 m (length) × 1.5 m (depth). The monitoring period for model calibration was the rainfall event during Aug. 31~Sep. 1, 2021 and the amount of rainfall was 74.5 mm. As a result of calibration, the determination coefficients (R²) of the flow rate were 0.66 and 0.86, for the inlet and outlet, respectively, and those of TSS loading were 0.50 and 0.84, for the inlet and outlet, respectively. Considering that ROADMOD is a screening level model, the calibration results were reasonable to evaluate the best management practices (BMPs) on the expressway. Using ROADMOD simulation results for 2012~2021, the average yearly runoff rate from the expressway was 82% and removal efficiency was 9% for road sweeping, 35% for sand filter facility, and 39% for both road sweeping and sand filter facility.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.6
• /
• pp.754-770
• /
• 1994

Suspended sediment distribution and water column processes in the upper Neuse River estuary, North Carolina, were monitored monthly from February 1988 through February 1989, in order to identify the turbidity maximum, to determine its temporal and spatial variation under changing conditions(freshwater runoff, wind, and tide). During most of the observation periods a weak turbidity maximum, associated with the estuarine circulation processes, developed at a flow convergence zone, near the upstream limit of salt intrusion. No turbidity maximum was found when the water column was vertically homogeneous with respect to salinity and when there was no consistent upstream bottom flow. Annual migration of the turbidity maximum, accompanied by migration of salt intrusion, was over 20 km of the upper estuary. Due to the coincidence of dominant wind direction(NE-SW) with the main orientation of the Pamlico-Neuse system, wind played the dominant role in dynamics of the turbidity maximum by influencing the degree of salinity stratification and the extent and strength of estuarine circulation. Tidal effects on the sediment dynamics were negligible.

• Journal of Korean Society on Water Environment
• /
• v.24 no.3
• /
• pp.365-377
• /
• 2008

Large artificial dam reservoirs and associated downstream ecosystems are under increased pressure from long-term negative impacts of turbid flood runoff. Despite various emerging issues of reservoir turbidity flow, turbidity modeling studies have been rare due to lack of experimental data that can support scientific interpretation. Modeling suspended sediment (SS) dynamics, and therefore turbidity ($C_T$), requires provision of constitutive relationships ($SS-C_T$) and accounting for deposition of different SS size fractions/types distribution in order to display this complicated dynamic behavior. This study explored the performance of a coupled two-dimensional (2D) hydrodynamic and particle dynamics model that simulates the fate and transport of a turbid density flow in a negatively buoyant density flow regime. Multiple groups of suspended sediment (SS), classified by the particle size and their site-specific $SS-C_T$ relationships, were used for the conversion between field measurements ($C_T$) and model state variables (SS). The 2D model showed, in overall, good performance in reproducing the reservoir thermal structure, flood propagation dynamics and the magnitude and distribution of turbidity in the stratified reservoir. Some significant errors were noticed in the transitional zone due to the inherent lateral averaging assumption of the 2D hydrodynamic model, and in the lacustrine zone possibly due to long-term decay of particulate organic matters induced during flood runoffs.

• Journal of Korean Society on Water Environment
• /
• v.26 no.3
• /
• pp.497-506
• /
• 2010

Severe muddy water problem has been the hot issue in Korea. Because of increased nonpoint source pollutions at Kangwon province, best soil erosion management system is required to reduce inflow of nonpoint source pollutions into the waterbodies. The USLE-based SATEEC system have been developed and enhanced for soil erosion and sediment yield estimation. However, the SATEEC cannot estimate soil depositions depending on topography in the watershed, while the USPED estimates soil erosion and deposition using sediment transport capacity of the surface runoff. In this study, the SATEEC and USPED were used to determine soil erosion hot spot subbasins. For this, 54 subbasins were delineated. In general, soil erosion hot spot subbasins were identified similarly with SATEEC and USPED. However, depending on erosion and deposition patterns in each subbasin. USPED estimated soil erosion hot spot subbasins didn't match those estimated with SATEEC. For some subbasins, much deposition was expected than erosion. This indicates that SATEEC estimated soil erosion values may be overestimated for these subbasins. Thus, care should be taken when understanding soil erosion status in the watershed based on USLE-based SATEEC results. In addition, the USPED results could be used to identify the site-specific soil erosion best management practices. If the USPED and USLE-based SATEEC are combined, it would help determining soil erosion hot spot subwatersheds in economic and environmental perspectives.

• Ecology and Resilient Infrastructure
• /
• v.8 no.4
• /
• pp.245-252
• /
• 2021

A turbidity current in a river and a lake occurs due to diverse nutrient loading including suspended sediment in sediment runoff, which affects water withdrawal and river environments. We developed one dimensional time-variant numerical model based on Python for the Nagdonggang mainstream. We examined the numerical stability and the applicability of the model by performing the simulation of quasi-steady flow in non-flooding for three cases, which are different according to the point and the amount of turbidity inflows in the Nagdonggang upstream and a tributary. The result was reasonable in the respect of the conservation of matter. The model will facilitate to simulate a large river if we can secure the data of turbidity variations in a target river reach or measured points in a field.

• Korean Journal of Soil Science and Fertilizer
• /
• v.31 no.3
• /
• pp.211-215
• /
• 1998

Soil loss and runoff were investigated in a small watershed located in Sangeo-ri, Yeoju-eup, Yeoju-gun, Kyonggi-do. The watershed with the area of 35 ha consists of forest, grassland, uplands and mulberry. V-notch type water tank. flow-meter, automatic water sampler and rain gauge were installed at the main outlet stream. Out of $1.037.9Mg\;35ha^{-1}$ of total annual rainfall. 17.9% was lost via run-off. The total amount of soil eroded was $152.2Mg\;35ha^{-1}$, of which $78.6Mg\;35ha^{-1}$ was suspended load and $73.6Mg\;35ha^{-1}$ ha was sediment load. The soil losses under different land uses were $16.02Mg\;ha^{-1}$ for upland annual Crops. $2.69Mg\;ha^{-1}$ for mulberry field, $0.58Mg\;ha^{-1}$ for grassland and $0.55Mg\;ha^{-1}$ for forest. The predicted soil loss by Universal Soil Loss Equation was approximately 20% underestimated in forest, grassland and uplands, and 32% underestimated in mulberry field.