The effect of landscape complexity on water quality in mountainous urbanized watersheds: a case study in Chongqing, China

The most significant feature of the landscape of mountainous urbanized watersheds is complexity. The geomorphology, composition, and configuration have strong ties with river water quality. In this study, through redundancy analysis, we examined how landscape complexity measured at both landscape and class levels related to water quality within watersheds. The results indicate that water quality is closely associated with both the relief degree of the land surface and patch density at the landscape level. The river water quality of mountainous watersheds is better if the relief degree of the land surface is larger, though river water quality degradation is associated with higher fragmentation of the landscape. At the class level, a greater proportion of non-urban land use may contribute to better river water quality, as do better connectivity and moderate degrees of aggregation. Water quality is more likely to be degraded when the shape of residential land, public service, and commercial land is more complex. We conclude that, in mountainous urbanized watersheds, river water quality can be protected through land use planning and management by regulating a set of landscape metrics for complexity measures.