Land cover and water yield: inference problems when comparing catchments with mixed land cover

Abstract

Abstract.Controlled experiments provide strong evidence that changing land cover (e.g. deforestation or afforestation) can affect mean catchment streamflow (Q). By contrast, a similarly strong influence has not been found in studies that interpret Q from multiple catchments with mixed land cover. One possible reason is that there are methodological issues with the way in which the Budyko framework was used in the latter type studies. We examined this using Q data observed in 278 Australian catchments and by making inferences from synthetic Q data simulated by a hydrological process model (the Australian Water Resources Assessment system Landscape model). The previous contrasting findings could be reproduced. In the synthetic experiment, the land cover influence was still present but not accurately detected with the Budyko-framework. Likely sources of interpretation bias demonstrated include: (i) noise in land cover, precipitation and Q data; (ii) additional catchment climate characteristics more important than land cover; and (iii) covariance between Q and catchment attributes. These methodological issues caution against the use of a Budyko framework to quantify a land cover influence in Q data from mixed land-cover catchments. Importantly, however, our findings do not rule out that there may also be physical processes that modify the influence of land cover in mixed land-cover catchments. Process model simulations suggested that lateral water redistribution between vegetation types and recirculation of intercepted rainfall may be important.

Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling

“…1) are part of a regional monitoring network named "Multi-Scale Environmental Change" (MSEC, http://msec.obs-mip.fr/), located in southeast Asia (Valentin et al, 2008b). They are exposed to a tropical climate influenced by the southwest monsoon bringing warm and humid air masses during the wet season (April-September), and by the northeast monsoon bringing colder dry air during the dry season (October-March).…”

Global analysis of seasonal streamflow predictability using an ensemble prediction system and observations from 6192 small catchments worldwide

“…Model predictions for Australia have been evaluated against remotely sensed time series of total terrestrial water storage Tregoning et al, 2012;Forootan et al, 2012;Van Dijk et al, 2013], surface soil wetness [Van Dijk and Warren, 2010;Doubkova et al, 2012], vegetation greenness [Van Dijk and Warren, 2010;Van Dijk et al, 2013], and vegetation cover fraction, leaf area, and surface albedo [Van Dijk and Warren, 2010]. The model has also been used in drought analysis and in examining the statistical detectability of land cover impacts on streamflow [Van Dijk et al, 2012b].…”

Assessing the Impact of Forest Change and Climate Variability on Dry Season Runoff by an Improved Single Watershed Approach: A Comparative Study in Two Large Watersheds, China

“…[1][2][3][4][5], consistent conclusions can hardly be drawn [6,7]. The effect of forest change on dry season flows can be positive, negative or insignificant [8].…”