Quantifying the relationship between water eutrophication and land use can help effectively manage land use to improve water quality. Previous studies principally utilized land use quantity as an indicator to link water quality parameters, but these studies lacked insight into the impact of land use intensity.  

ZHANG Hongqi, associate professor and his group from Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences, developed a method of aggregating land use quantity and intensity to build a new land use indicator and tested its explanatory power on water quality. 

Based on spatial techniques, empirical conversion coefficients, remote sensing data, and socio-economic statistical data, researchers measured and mapped visually land use intensity. The new land use indicator was calculated and linked to nutrient concentrations by Pearson correlation coefficients.  

 “We calculated the land use intensity for each cell at the countryside scale and aggregated the land use quantity and intensity at the sub-watershed scale. Compared to previous studies only using the quantitative structure of land use, our method quantified spatial land use intensity to discriminate the nutrient export ability within the same land use types.” Dr. ZHANG said. 

The results demonstrated that the new indicator incorporating intensity information can quantify the different nutrient-exporting abilities of different land use areas.  

This new information enhanced the explanatory power of land use on water nutrient concentrations, and so will be able to help us understand the impact of land use on water quality and guide decision making for better land use management.  

Related research results have been published in Ecological Indicators (Erqi Xu, Hongqi Zhang. Aggregating land use quantity and intensity to link water quality in upper catchment of Miyun Reservoir. Ecological indicators. 2016. 66: 329-339.). 

Conceptual framework of aggregating land use quantity and intensity (Image by ZHANG Hongqi)