基于可解释机器学习的洱海北部流域溶解氧驱动因素分析与改善策略OA

[Objective]Dissolved oxygen(DO)is a key indicator for evaluating water environmental quality,low DO concentration in rivers disrupts ecological balance and threatens aquatic ecosystem health.This paper models and predicts DO concentrations,identifies the key factors driving its variations,and proposes essential measures for regulating water quality and protecting aquatic ecosystems.[Methods]Based on water quality and quantity monitoring datas from the northern Erhai Lake Basin from 2011 to 2020,this paper constructed an integrated machine learning framework,established and selected the optimal model-light gradient boosting machine model(LightGBM)for predicting changes in DO.Furthermore,this paper employed Shapley additive explanations(SHAP)to quantify the contributions of different features to the variation in DO concentration.[Results]The coefficient of determination(R2)for the LightGBM model improved by 11.2％compared to the baseline model,demonstrating superior predictive performance[root mean square error(RMSE)=0.284 mg/L,mean absolute error(MAE)=0.226 mg/L,R2=0.912].SHAP analysis revealed that flow rates emerged as the dominant influencing factor(35.5％),followed by chemical oxygen demand(COD)(17.2％).DO levels initially increased and then decreased with rising flow rates:moderate flow rates enhanced oxygenation,while excessive flow rates introduced a large amount of oxygen-consuming pollutants,thus reducing DO.Suitable flow rates and low COD were identified as key conditions for maintaining high DO concentrations,a flow rate of 0.2 m3/s was recommended,and achieving the lowest possible COD level was crucial.[Conclusion]In the study areas,both high summer flows and low winter flows(or flow interruption)lead to decreased DO concentration.Regulating water storage and purification using reservoirs and ponds along the basin can stabilize flow rates,reduce runoff pollution,and sustain DO levels.This paper enhances understanding of flow-dependent DO dynamics and provides a scientific basis for ecological conservation in plateau river systems.