Influences of land use metrics at multi-spatial scales on seasonal water quality: A case study of river systems in the Three Gorges Reservoir Area, China

Abstract The impact of land use metrics on watershed water quality is scale-dependent on a seasonal - spatial basis. Exploring the associations between land use metrics and riverine water quality provides useful information for effective land use planning for water quality security, whilst, these relationships remain poorly understood. 94 water samples covering entire tributaries in the Three Gorges Reservoir Area were collected and analyzed over the time period of 2015–2016, and consequently, multivariate statistics and empirical models were used for understanding the associations between land use metrics and water quality across multi-scales. Analysis of variance (ANOVA) revealed significant spatial differences in water temperature (WT), potential of hydrogen (pH), dissolved oxygen (DO), total nitrogen (TN), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), TDN/TDP, nitrate nitrogen (NO 3 − -N), ammoniacal nitrogen (NH 4 + -N) and permanganate index (COD Mn ). Meanwhile, Oxidation-Reduction Potential (ORP), electrical conductivity (EC), DO, TN, TDN, TP, TDP, NO 3 − -N, NH 4 + -N and COD Mn generally appeared higher values in the dry season. Redundancy analysis (RDA) showed that the total explained variation of land use metrics on overall water quality was slightly stronger at catchment scale than at 100 m and 500 m buffer scales. The influence of land use metrics on water quality was a little stronger in the dry season than the wet season, but there were multi-spatial scale effects of different land use metrics. Our results can provide important information in land use planning and making multiple scales measures for water quality conservation.