Yajiao Li

Evaluation of AnnAGNPS and its applications in a semi-arid and semi-humid watershed in Northwest China

The main goal of this study was to evaluate the performance of AnnAGNPS (Annualised Agricultural Non-Point Source Pollution Model) in simulating runoff, sediment loading and nutrient loading in a semi-arid and semi-humid watershed of an area of 1481sq km, located in Northwest China. This model was first calibrated and tested by historic monitoring data and then the validated model was used to simulate the effects of non-point source (NPS) pollution management measures. The results indicate that reforestation measures, which reduce the amount of runoff, sediment, total nitrogen and total phosphorus, should be adopted in the study watershed to control NPS pollution. The model was also used to assess the effects of other measures on NPS pollution. This study concludes that AnnAGNPS has the potential to be a valuable tool for the planning and management of watersheds in the semi-arid regions of China.

Hydrological Environmental Responses of LID and Approach for Rainfall Pattern Selection in Precipitation Data-Lacked Region

Global climate change and urbanization development have changed the hydrological environment dramatically. Flood control, non-point source pollution control, and comprehensive utilization of water resources are facing new challenges. On the basis of the Storm Water Management Model (SWMM), an approach for design rainfall pattern selection in precipitation data-lacked region containing model establishing, response analysis and design rainfall pattern screening was put forward. And the responses of the hydrologic, hydraulic and environmental of 2-commercial community mode are explored by using a simulation analysis under different rainfall patterns in this study. Based on the worst principle, the Chicago rainfall pattern was selected for the above-mentioned evaluation indexes at different reoccurrence periods. Results showed that, (1) in traditional development (TD), the values of surface runoff, peak flow and depth of outlet, and total pollution loading were at their maximum at the Chicago rainfall pattern; and in low-impact development (LID), the reduction rates of surface runoff and total pollution loading were at their minimum at the Huff4 rainfall pattern, and the reduction rate of peak flow was at its minimum at the P&C rainfall pattern; then design storm patterns at different simulation targets were obtained. (2) For the Chicago rainfall pattern, the reduction rates of various evaluation indexes decreased while the reoccurrence period increased, and the reduction rate of peak flow was more sensitive to high reoccurrence period rainfall than surface runoff. (3) After the setting of LID measures, the control effect of storm water and non-point source pollution gathered better results from the increase of permeable area and the change of microtopography, as well as from the physical and biological action. This study will provide a reference for the selection of design storm pattern at different simulation targets in regions with deficient rainfall data.

Modeling the effects of parameter optimization on three bioretention tanks using the HYDRUS-1D model

The operation effects of bioretention on different tanks were investigated through tests and simulations. Three layered bioretention tanks, namely, #1, #2, and #3, were selected for intermittent operation tests. The artificial filler layers of the tanks consisted of mixed fillers of fly ash and sand, blast furnace slag, and planting soil. Models were established by using HYDRUS-1D software based on test results. The sensitivity of model parameters was analyzed through Morris screening method. Results showed that return period, thickness of media layer, and solute concentration in the liquid phase were the parameters that significantly influenced the operation effects. The Nash-Sutcliffe efficiency coefficients of the models were greater than 0.85. The simulation results showed that the reduction effects at different inflow loads were better under low loads than under high loads. The comprehensive reduction rate of pollutant load was 5.22% less under high concentrations than under low concentrations. The comprehensive reduction rates of water and pollutant loads were 35.97% and 20.68% greater, correspondingly, in the 1 year return period than in the 10 year return period. The artificial fillers comprising a mixture of fly ash and sand also showed the optimal reduction effects, with comprehensive reduction rates of 69.33% and 83.08% for water and pollutant load, respectively. The reduction effects of water and pollutants for the #1 tank presented an upward trend, whereas those for the #2 tank showed a downward trend given an increase in planting soil thickness. An increase in media thickness enhanced the reduction effects. The media with 60 cm thickness demonstrated the optimal effect.

Experimental study and simulation of phosphorus purification effects of bioretention systems on urban surface runoff

Excessive phosphorus (P) contributes to eutrophication by degrading water quality and limiting human use of water resources. Identifying economic and convenient methods to control soluble reactive phosphorus (SRP) pollution in urban runoff is the key point of rainwater management strategies. Through three series of different tests involving influencing factors, continuous operation and intermittent operation, this study explored the purification effects of bioretention tanks under different experimental conditions, it included nine intermittent tests, single field continuous test with three groups of different fillers (Fly ash mixed with sand, Blast furnace slag, and Soil), and eight intermittent tests with single filler (Blast furnace slag mixed with sand). Among the three filler combinations studied, the filler with fly ash mixed with sand achieved the best pollution reduction efficiency. The setting of the submerged zone exerted minimal influence on the P removal of the three filler combinations. An extension of the dry period slightly promoted the P purification effect. The combination of fly ash mixed with sand demonstrated a positive purification effect on SRP during short- or long-term simulated rainfall duration. Blast furnace slag also presented a positive purification effect in the short term, although its continuous purification effect on SRP was poor in the long term. The purification abilities of soil in the short and long terms were weak. Under intermittent operations across different seasons, SRP removal was unstable, and effluent concentration processes were different. The purification effect of the bioretention system on SRP was predicted through partial least squares regression (PLS) modeling analysis. The event mean concentration removal of SRP was positively related to the adsorption capacity of filler and rainfall interval time and negatively related to submerged zones, influent concentration and volume.