In this study, the relationship between hydrological characteristics and phytoplankton biomass (chlorophyll a concentration) was explored using long-term hydrological and limnological data (1994–2007) in a flow-regulated river system (the lower Nakdong River, South Korea). This river has four multi-purpose dams and an estuarine barrage, and river flow is extensively controlled. Dynamics of chlorophyll a concentration responded well to changes in hydrology, such as rainfall, dam discharge and river flow. The hydrological characteristics strongly affected the decrease of chlorophyll a concentration in summer to winter but not in spring (p<0.05; n=42). An application of Self-Organizing Map (SOM) model to the database returned three clusters, and strong seasonality in water quality as well as hydrological characteristics was identified. Long-term rainfall data exhibited no statistical tendencies of increase or decrease, with respect to total annual rainfall. In comparison, summer rainfall increased while that of winter (December to the following February) decreased. Summer rainfall affected total dam discharges in all seasons in a positive manner (p<0.05; n=14), corresponding to winter water quality of the lower Nakdong River likely to be dependent largely upon changes in summer rainfall. Therefore, the development of an effective management strategy for summer rainfall and dam discharge control is strongly required.

Impermeable materials are used for parking lots at apartment complexes and large stores which are concentrated in urban areas. These materials increase the amount of surface runoff by blocking infiltration, resulting in flood damage, dry stream phenomena in rivers in urban watersheds, and the depletion of ground water. In this study, a parking lot plot was constructed to quantitatively evaluate the efficiency of pavements using various materials (impermeable concrete, permeable concrete, and permeable block pavement). Four scenarios of rainfall intensity were simulated using a rainfall simulator within each plot (36 mm h⁻¹, 48 mm h⁻¹, 60 mm h⁻¹, 72 mm h⁻¹). The flow was observed by monitoring the system with a bucket flow meter. The efficiency and flow characteristics of the permeable concrete and block pavement were analyzed. The results were used to calculate the ratio of the surface flow to the infiltrating flow between impermeable and permeable pavements. The permeable concrete had a ratio of 1:0.9, and the permeable block pavement had a ratio of 1:0.58.

Low Impact Development (LID) techniques have been drawing an increasing attention in recent years as efficient ways of stormwater management. These methods try to mimic nature by providing pervious area which has been decreased due to urbanization. One of the most efficient practices of LID is the use of Green Roof (GR) systems. Although GRs have been traditionally used in the past, their engineering design and construction is a recent trend. Since GR systems, similar to other LID techniques, are supposed to endure local climate and environmental conditions, their design should be accomplished regarding the conditions of the area where they will be installed. In order to systematically examine, design, and construct various LID techniques for Korean climate and environment, the LID & GI Center of Korea is built in Pusan National University. This center tries to hire hardware and software facilities to study and design LID practices; Hydrological Performance Tester for Green Roof (HPT-GR) and Korea Low Impact Development Model (K-LIDM) are made for this purpose. In order to examine the performance of a Green Roof (GR) system composed of layers with different material and size, five trays were made at LID & GI Center of Korea. The size and composition of these trays were: (A) plant + soil + drainage mat with total depth of 15 cm, (B) plant + soil + sand with total depth of 15 cm, (C) plant + soil + sand with total depth of 9 cm, (D) a bare soil with total depth of 15 cm, and (E) a concrete with total depth of 15 cm. All the trays were examined under different uniform precipitations with rates of 50, 80, 100 and 150 mm/h using HPT-GR. The results showed that the use of drainage mat in tray A could significantly improve the performance of the GR by increasing its storage capacity up to 40% of the rainwater, decreasing its saturation rate, and reducing its discharge peak value. Then, as the first use of K-LIDM for simulating a green roof, all the experimental GRs were numerically simulated using this model; the numerical hydrographs were compared to those achieved from the experiment. The results showed that K-LIDM can be used for performance prediction of GR systems with slightly conservative but acceptable results. With an increase in the rainfall intensity, the discharge peak values increased and their times decreased in both numerical and experimental scenarios; however, the peak values were slightly higher in simulation results than those of the corresponding experimental ones.

The amount of non-point pollutants discharged into rivers is greater in urban regions than forests and farmlands due to a higher population density and a larger impermeable area. The analysis and research of non-point pollution in urban areas have been focused upon monitoring the basin outlets, and estimating the environmental loads as well as the unit load. However, the estimation based on the measurements of a single representative spot in the large basin is often calculated, compared to the measurements based on the area and the land use. A less credible method to estimate the load cannot be effectively used in quantifying the non-point pollutant loads caused by the individual land uses. Therefore a method that segments the basin according to the land use in the urban region is required. This is the key to a credible quantified analysis of non-point pollutant loads and enables a rational and scientific estimation of significance, cut rate, and establishing reduction plans. The goal of this research was to estimate the load with segmenting the urban region into different sections based on the land use and constructing a model that reflects the traits of each section. The data was compiled by observations of the Busan City separated into residential districts, business districts, industrial districts, and greens. SWMM was used to simulate the target area, while attempts to compare it with prior researches were made to evaluate the validity and applicability of this research and to ensure its credibility.

Various techniques are being developed and applied for the management of non-point pollutants. Especially, there has been an increasing interest in the techniques which work for both the restoration of hydrologic cycle and management of non-point pollutants. When the need for the management of non-point pollutants first arose, structural concept of BMP was developed. Recent years saw the expansion of management plans including precautionary land use techniques such as low impact development (LID). LID is usually applied to new development areas but lately is in extensive use with existing city areas. To analyze the effect of LID application on an industrial complex by using Strom Water Management Model (SWMM), a point with clear division of the soil pipe and rainwater pipe sections was selected for monitoring non-point pollutant runoff and analyzing the characteristics of the runoff in this study. Furthermore, to construct a SWMM-LID model of a small-scale catchment, RUNOFF blocks were subdivided into sections and six event data with satisfactory flow pattern were selected from 24 monitoring data collected over three years (2009–2011) to be calibrated, two more event data were used for verification to complete the construction of the model. LID key technologies were applied as four CASEs: existing condition of the city (CASE 1), application of rain barrel (CASE 2), rain barrel and tree filter box (CASE 3), rain barrel, tree filter box, and porous pavement (CASE 4) for short-term and long-term (seasonal) simulation analyses.

Water quality control is affected by several factors such as climate change or the creation of an ecological park for human convenience. The Four-River restoration project of Korea is a government enterprise to solve a variety of problems, such as preventing floods, securing water resources, water quality management, and encouraging re-creation of land. It is evidence that technical developments and the concern of the government have sharply increased for water quality management. In particular, the phenomenon of eutrophication can cause various difficulties in drinking water treatment and water use. Accurate and reliable algal bloom forecasting models will prove very useful in ensuring sustainable water supply and proper water management in the near future. In this paper, a new method based on wavelet transforms and artificial neural networks was adopted for chlorophyll-a concentration forecasting 1, 3 and 7 days ahead. First, 12 models for forecasting chlorophyll-a concentration by combining water quality and hydrological factors from different models as input data were established by using an original ANN with a back-propagation algorithm. The best model, as evaluated by its performance functions, was selected and applied to the new method as a coupled wavelet analysis-artificial neural network (WA-ANN) to forecast chlorophyll-a concentration for 1, 3 and 7 days. Finally, the results of WA-ANN in the study were compared to those of a regular ANN with a back-propagation algorithm. The results showed that WA-ANN models constitute a promising new method for short-term chlorophyll-a concentration forecasting in large lakes.