Steady-state Water Quality Model Research Articles

Eutrophication forcings on a peri-urban lake ecosystem: Context for integrated watershed to airshed management.

Peri-urban lakes increasingly experience intensified anthropogenic impacts as watershed uses and developments increase. Cultus Lake is an oligo-mesotrophic, peri-urban lake near Vancouver, British Columbia, Canada that experiences significant seasonal tourism, anthropogenic nutrient loadings, and associated cultural eutrophication. Left unabated, these cumulative stresses threaten the critical habitat and persistence of two endemic species at risk (Coastrange Sculpin, Cultus population; Cultus Lake sockeye salmon) and diverse lake-derived ecosystem services. We constructed water and nutrient budgets for the Cultus Lake watershed to identify and quantify major sources and loadings of nitrogen (N) and phosphorus (P). A steady-state water quality model, calibrated against current loadings and limnological data, was used to reconstruct the historic lake trophic status and explore limnological changes in response to realistic development and mitigation scenarios. Significant local P loadings to Cultus Lake arise from septic leaching (19%) and migratory gull guano deposition (22%). Watershed runoff contributes the majority of total P (53%) and N (73%) loads to Cultus Lake, with substantial local N contributions arising from the agricultural Columbia Valley (41% of total N load). However, we estimate that up to 66% of N and 70% of P in watershed runoff is ultimately sourced via deposition from the nutrient-contaminated regional airshed, with direct atmospheric deposition on the lake surface contributing an additional 17% of N and 5% of P. Thus, atmospheric deposition is the largest single source of nutrient loading to Cultus Lake, cumulatively responsible for 63% and 42% of total N and P loadings, respectively. Modeled future loading scenarios suggest Cultus Lake could become mesotrophic within the next 25 years, highlighting a heightened need for near-term abatement of P loads. Although mitigating P loads from local watershed sources will slow the rate of eutrophication, management efforts targeting reductions in atmospheric-P within the regional airshed are necessary to halt or reverse lake eutrophication, and conserve both critical habitat for imperiled species at risk and lake-derived ecosystem services.

Parameters sensitivity analysis of DO in water quality model of QUAL2K

QUAL2K is a comprehensive longitudinal one-dimension steady-state water quality model, which considers the effect on dissolved oxygen (DO) through nitrogen circulation, algae growth and sediment oxidation process. And this model integrated hydrological model and temperature model, so it is widely adopted in the overseas. Because of its complexity and multiple parameters, the application of this model is restricted in China. Parameters optimization is inevitable in the usage of the water quality model. The modified Morris screening method is used and DO is selected as study index to proceed sensitivity analysis and further optimize related parameters. The high sensitive parameters, sensitive parameters and low sensitive parameters are determined.

Study on the Water Environmental Capacity and the Sewage Control of the Sushui River

In order to know the environmental capacity, improve the continual deterioration of the water quality in Sushui River, and promote the harmonious development of economy and aquatic environment, we did the following research. Based on the 1-D steady-state water quality model, the outfalls are generalized, and then we derived the formula for calculating water environmental capacity of each reach. According to the information of water quality, hydrology data and the discharge distribution of the river, we chose COD, ammonia nitrogen and volatile phenol as the main control factors, and some formulas were used to calculate the water environmental capacity of COD, ammonia nitrogen and volatile phenol. From which we got that annual water environmental capacity of COD, ammonia nitrogen and volatile phenol on the studied reach respectively arrive at 1257.897~1420.928t, 17.873~26.025t and 1.750~2.871t under different design terms. It is serious pollution in the Sushui River, combined with the status quo emissions, we found that under different design terms, the annual quantity of pollutants reduction of COD, ammonia nitrogen and volatile phenol arrive at 30.36×106t, 3.257×106t and 0.1745×106t.

Estimation of Water Environmental Capacity Considering Hydraulic Project Operation in the Xiangyang Reach of the Han River, Central China

Using the Xiangyang Reach of the Han River as an example, this paper evaluates the changes of water environmental capacity after the implementation of Cuijiaying Hydro-junction project. The allowable pollutant loads entering the Xiangyang Reach were estimated using two-dimensional steady state water quality model with different data sets. The water environmental capacity has declined in the reservoir area of the Cuijiaying Hydro-junction project during the low-flow period; it is appearing to increase slightly in the upper and lower stream of this reservoir. However, the state of flow may turn into the state of reservoirs flow in the reservoir area, and the changes of hydrological regime may cause the water flow and the nutrient contents suitable for the occurrence of ecological environment problems.

The influence of artificial cutoff on a monitoring system and the water quality of the Keelung River

The purpose of this study was to design a water quality monitoring network for the Keelung River in order to evaluate the effects of artificial cutoff across two bend channels. A steady-state water quality model was used to simulate the BOD and DO curves. The Kriging theory was applied to select the optimal locations for a water quality monitoring network. The sampling frequency was determined by the coefficients of variation of water quality and by considering the significance level and confidence interval. After calibration and verification of the water quality model, the model was applied and the simulation results indicated that the values of DO in the new channel would be higher than those of the old channel reaches. The critical point of the oxygen sag curve would shift to the mouth of river under O75 low-flow conditions, and the BOD values in the new channel would also slightly increase. The results further indicated that more monitoring stations would be needed in the downstream reaches.

The identifiability of parameters in a water quality model of the Biebrza River, Poland

The identifiability of model parameters of a steady state water quality model of the Biebrza River and the resulting variation in model results was examined by applying the Monte Carlo method which combines calibration, identifiability analysis, uncertainty analysis, and sensitivity analysis. The water quality model simulates the steady state concentration profiles of chloride, phosphate, ammonium, and nitrate as a function of distance along a river. The water quality model with the best combination of parameter values simulates the observed concentrations very well. However, the range of possible modelled concentrations obtained for other more or less equally eligible combinations of parameter values is rather wide. This range in model outcomes reflects possible errors in the model parameters. Discrepancies between the range in model outcomes and the validation data set are only caused by errors in model structure, or (measurement) errors in boundary conditions or input variables. In this sense the validation procedure is a test of model capability, where the effects of calibration errors are filtered out. It is concluded that, despite some slight deviations between model outcome and observations, the model is successful in simulating the spatial pattern of nutrient concentrations in the Biebrza River.

Water quality monitoring network design of keelung river, northern taiwan

The purpose of this study was to design the water quality monitoring network of the Keelung River which was channel regulated recently. A steady-state water quality model was used to simulate the BOD and DO curves. Kriging theory was applied for selecting the optimal locations of water quality monitoring network. The sampling frequency was determined by variances of water quality, considering the significant level and confidence interval. The optimal results indicated that more monitoring stations are needed in the downstream reaches. The stations suggested in the total number of monitoring network of the Keelung River is twenty-one, and the sampling frequency needs to be about two or three times per month.

Water quality monitoring network design of Keelung River, Northern Taiwan

The purpose of this study was to design the water quality monitoring network of the Keelung River which was channel regulated recently. A steady-state water quality model was used to simulate the BOD and DO curves. Kriging theory was applied for selecting the optimal locations of water quality monitoring network. The sampling frequency was determined by variances of water quality, considering the significant level and confidence interval. The optimal results indicated that more monitoring stations are needed in the downstream reaches. The stations suggested in the total number of monitoring network of the Keelung River is twenty-one, and the sampling frequency needs to be about two or three times per month.