Attributes Of River Water Quality Response To Climate Drivers Based On Climate Elasticity Approaches

This research work was conducted to investigate the sensitivity of river water quality parameters to changes in precipitation and air temperature and instability consequences caused by nonclimatic factors.This research performs sensitivity analyses using elasticity principle from microeconomics(i.e.,price elasticity of demand)to uncover climate-water quality relationships.Here,the concept of elasticity is implemented in a water quality context to identify the sensitivity of main water quality parameters at global scale using bivariate and multivariate approaches.The novelty of this research work is the introduction of elasticity approach which is handy for global studies where it is difficult to define physically based water quality/hydrologic models which suite large watersheds of the world,and to acquire datasets for such models.General observations on elasticity values show the usefulness of this approach to describe the magnitude of stream water quality responses to climate change at global scale,which overwieghs simple statistical correlation.Precipitation elasticity is highly variable in space as compared to temperature elasticity.Precipitation elasticity shows prominent seasonality.Simply this technique is handy in exposing the response of water quality parameters to climatic drivers at global scale.Furthermore,the response of total nitrogen and water temperature is prominent to air temperature as compared to precipitation.Particullary,significant decreasing trends were observed at Yukon and Murray watersheds for majority water quality parameters except turbidity and filtered Nitrate plus Nitrite respectively while increasing trends were exhibited by majority water quality parameters at Mekong watershed.In comparison to Yukon and Murray(except filtered Nitrate plus Nitrite and unfiltered total nitrogen)watersheds,probability distributions of majority water quality parameters and its corresponding percentage change based 'sample' of elasticity estimator are characterized by heavy tailed distribution at Mekong watershed.Precipitation elasticity results are statistically meaningful at Mekong and Murray watersheds while temperature elasticity is statistically significant at Yukon watershed.The stability of CEWQ is highly dependent on terrestrial determinants,with strong impacts from anthropogenic biomes and low impact from surficial geology.In comparison to temperature elasticity,precipitation elasticity of water quality is more unstable due to its possible linkages with many terrestrial determinants.Correlation and linear models were developed for the interaction system,which uncovered many interesting rules.The results implied that watersheds with higher ratio of rangeland biomes have lower risk of instability as compared to watersheds with higher proportion of dense settlement,cropland and forested biomes.Precipitation elasticity shows higher sensitivity to topographic and socio-economic determinants as compared to temperature elasticity.In Northern Hemisphere,CEWQ of Nitrogen parameters and unfiltered Phosphorus showed higher risk of instability due to runoff coefficient and slope,and gross domestic product(GDP)respectively.In contrast,stability was observed in dissolved oxgen(DO)owing to runoff coefficient and Nitrogen fertilizer in Southern Hemisphere.In tropical climate class(A),GDP played friendly role in stabilizing the CEWQ.In temperate climate class(C),GDP revised the same role of stability while runoff coefficient,slope,and population density fuel the risk of instability.The results implied that watersheds with lower runoff coefficient,thick population density,over fertilization and manure application face a higher risk of instability.Soil moisture brings stability while relative humidity and CO2 produce instability consequences in CEWQ parameters at global scale.In Northern Hemisphere,the risk of instability was declined by soil moisture.Soil moisture brings stability,CO2 produce instability and relative humidity played dual role in Southern Hemisphere.Soil moisture played stabilizing role in tropical(A)& dry climate class(B)while relative humidity performed destabilizing role in climate class(B).In temperate climate class(C),interestingly wind speed performed dual role while CO2 played the same role of instability.This research work introduces new concept of elasticity for water quality modeling and improves our understanding of the climate-water quality relationships at global scale.It discussed some of the most essential pathways where instability may adversely affect CEWQ parameters due to terrestrial,socio-economic and environmental determinants,and recommended suggestions for policy makers to alleviate the instability‘s impacts to bring sustainability in water environment.