A Comparative Study Of Changes In The Water Environment Of 2 Lakes In Jiuzhaigou

Strengthening the construction of wetland parks in the context of urbanisation not only helps to protect the urban ecological environment and promote sustainable development,but also enables people and nature to co-exist in harmony.In landscape gardening practice,the characteristics of the wetland water environment often become a decisive influence on the quality of wetland park construction.Based on this,the thesis takes two wetland lakes with distinctly different plant composition in the Jiuzhaigou scenic area,a natural heritage site,as the target,and monitors the physical and chemical parameters of water quality in the field and in the laboratory between June 2021 and June 2022.The main findings of the study are as follows:（1）The plant composition of the Reed Lake under study is dominated by a single dominant species of the jerkin reed community,with a few random companion species occurring along the shore,and the average cover of the reed community in the Reed Lake is greater than 75%,with some sample sites reaching 100%reed cover;the Double-dragon Lake under study shows very few aquatic plants in the water and no obvious dominant species in the wetland.（2）The water environment of the two wetland lakes has obvious characteristics of daily dynamic change,and the trend of daily dynamic change of water quality is not consistent with seasonal changes.p H and DO concentration basically have the same daily change pattern,combined with the water temperature and DO change trend of each sampling point in Reed Lake Wetland and Double-dragon Lake Wetland within a day,the two wetland lakes change trend is basically the same,with the water temperature of a day increases so that DO concentration also increases.The DO concentrations in the two wetland lakes were generally consistent,with DO concentrations increasing as the water temperature increased during the day,and decreasing as the water temperature decreased until the evening.COD and TOC concentrations fluctuate from season to season,and there is no obvious pattern,while TN and TP concentrations in the two wetland lakes do not vary significantly from one day to the next,and the main changes need to be analysed in terms of seasonal changes.（3）The environmental indicators of Double-dragon Lake have obvious temporal characteristics with seasonal changes.The overall water temperature of the plateau wetland lakes is low,showing a trend of high summer and low winter with the seasons,with a range of 5.2～14.4°C;the water is weakly alkaline,with p H showing high in spring and summer and low in autumn and winter,with a range of 6.2～8.56;DO showing high summer and low winter,with a range of 6.82～15.95 mg/L;EC did not change significantly with the season,with a range of 329～367μS/cm;TOC concentration showed a high spring and low winter,with a range of 0.02～0.53 mg/L;COD concentration showed a trend of high summer,low winter and low spring with the season,with a range of 9.23～44.94 mg/L;nitrogen and phosphorus nutrients showed a consistent trend,with an overall high summer and low winter,with a range of TP concentration 0.0042～0.0053 mg/L,TN concentration range 0.11～1.30mg/L;NO₃^--N trend was high in winter and low in spring,with concentration range0.01～0.08 mg/L;K⁺concentration range 0.44～0.64 mg/L,Na⁺concentration range0.92～1.80 mg/L,Mg²⁺concentration range 8.41～13.42 mg/L,The environmental variation of Reed Lakewater was also consistent with that of Double-dragon Lake over the seasons,with water temperature ranging from 6.6～13.4°C,p H ranging from 6.35～8.16,DO varying from 5.83～14.33 mg/L,EC varying from 310～392μS/cm,TOC ranged from 0.01～1.03mg/L,COD varied from 10.03～27.47 mg/L,nitrogen and phosphorus nutrients varied in the same trend,TP concentrations ranged from 0.038 to 0.051 mg/L,TN concentrations ranged from 0.13～1.29 mg/L,NO₃^--N concentrations ranged from 0.01～0.08 mg/L;K⁺concentrations ranged from 0.45～0.71 mg/L,Na+concentration range 0.98～1.59 mg/L,Mg²⁺concentration range 9.05～13.39 mg/L,Ca²⁺concentration range 44.69～52.20 mg/L.（4）The water quality of the Reed Lake and the Double-dragon Lake wetland was compared by principal component analysis and Nemero index comprehensive analysis,and the analysis concluded that the reed community has an impact on the water quality of the wetland lake.When the reeds are growing vigorously in summer,their cover reaches 75%,and even close to 100%in some areas,which makes the water temperature lower than that of the Double-dragon Lake wetland,and the plants carry out photosynthesis and absorb nutrient salts,which have an impact on the water environment,making the wetland The DO and COD concentrations in the water are lower than in the Double-dragon Lake,and the nitrogen and phosphorus nutrients are lower than in the Double-dragon Lake.In winter,the reed plants wither in the water,and the leaves fall and humus accumulates,causing the water temperature to rise and the decomposition of humus to consume oxygen and produce acidic metabolites.An analysis of the water environment during the peak of the reed growth period and the reed wilting period shows that reed community planting can effectively clean the water environment of the wetland during the growth period.However,it is necessary to harvest the fallen leaves and dead branches in time when the reed wilts in winter to prevent organic matter such as reed humus from flowing into the water and polluting the water environment of the wetland.In addition,the high density of reed plants in the summer prevents the water body from directly exchanging substances with the atmosphere and reduces the concentration of dissolved oxygen,which has a negative impact on the water environment.A comparative analysis of the spatial and temporal variability of two natural wetland lakes is conducted to explore the influence of reed plant communities on the dynamic changes in water quality.The study aims to provide a reference basis for the construction of urban artificial wetlands.