Uncertainty analysis of a spatially explicit annual water-balance model: case study of the Cape Fear basin, North Carolina

Abstract

Abstract. There is an increasing demand for assessment of water provisioning ecosystem services. While simple models with low data and expertise requirements are attractive, their use as decision-aid tools should be supported by uncertainty characterization. We assessed the performance of the InVEST annual water yield model, a popular tool for ecosystem service assessment based on the Budyko hydrological framework. Our study involved the comparison of 10 subcatchments ranging in size and land-use configuration, in the Cape Fear basin, North Carolina. We analyzed the model sensitivity to climate variables and input parameters, and the structural error associated with the use of the Budyko framework, a lumped (catchment-scale) model theory, in a spatially explicit way. Comparison of model predictions with observations and with the lumped model predictions confirmed that the InVEST model is able to represent differences in land uses and therefore in the spatial distribution of water provisioning services. Our results emphasize the effect of climate input errors, especially annual precipitation, and errors in the ecohydrological parameter Z, which are both comparable to the model structure uncertainties. Our case study supports the use of the model for predicting land-use change effect on water provisioning, although its use for identifying areas of high water yield will be influenced by precipitation errors. While some results are context-specific, our study provides general insights and methods to help identify the regions and decision contexts where the model predictions may be used with confidence.

Effect of National-Scale Afforestation on Forest Water Supply and Soil Loss in South Korea, 1971–2010

“…The seasonality constant (Z) was estimated as 0.2 × N, where N is the average number of rainy days (>1 mm) per year over the study period [39,40]. N was estimated at approximately 80 from our KMA dataset, resulting in a value of 16 for Z.…”

Empirical validation of the InVEST water yield ecosystem service model at a national scale

“…Kc and Z following Sánchez-Canales et al (2012) and Hamel and Guswa (2015). The biophysical 216 parameters, which are input as rasters, were varied by ± 10% and ± 20% applied uniformly across the 217 raster.…”

The impact of roads and sediment basins on simulated river discharge and sediment flux in an experimental catchment designed to improve ecosystem services

“…On the other hand, most modelling studies of sediment delivery and streamflow did not considered the presence of roads in their land use maps or they did not approach the issue of their effect on hydraulic connectivity, for changing the original path of water (e.g. Bangash et al, 2013;Hamel and Guswa, 2015;San, 2015;Strauch et al, 2013;Terrado et al, 2014).…”

“…Conservation Project) was the first PES municipal experience in the Country, located in the municipality of Extrema, in the State of Minas Gerais, motivated by the known relationship between forests and water conservation, and the growing anthropic pressure around Cantareira system's water reservoirs that supply about 50 % for the Sao Paulo processes are sometimes difficult to obtain, the lack of comparison with observed data and inadequate validation jeopardize its use (Hamel and Guswa, 2015). Posses watershed was the first to be part of Conservador das Águas project, with the lowest forest conservation levels at the time of its implementation (Kfouri and Favero, 2011).…”

“…Pasture K c was achieved by calibration. Z parameter was estimated by the number days of rain divided by 5 (Hamel and Guswa, 2015), which resulted in 25.…”