scholarly journals Uncertainty analysis of a spatially-explicit annual water-balance model: case study of the Cape Fear catchment, NC

2014 ◽  
Vol 11 (10) ◽  
pp. 11001-11036 ◽  
Author(s):  
P. Hamel ◽  
A. J. Guswa
Keyword(s):  
Land Use ◽  
Water Balance ◽  
Water Balance Model ◽  
Balance Model ◽  
Water Yield ◽  
Model Structure ◽  
Model Predictions ◽  
Cape Fear ◽  
Annual Water

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 framework. Our study involved the comparison of ten subcatchments in the Cape Fear watershed, NC, ranging in size and land use configuration. We analyzed the model sensitivity to the eco-hydrological parameters and the effect of extrapolating a lumped theory to a fully distributed model. Comparison of the model predictions with observations and with a lumped water balance model confirmed that the model is able to represent differences in land uses. Our results also emphasize the effect of climate input errors, especially annual precipitation, and errors in the eco-hydrological parameter Z, which are both comparable to the model structure uncertainties. In practice, 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 the results are inherently local, analysis of the model structure suggests that many insights from this study will hold globally. Further work toward characterization of uncertainties in such simple models will help identify the regions and decision contexts where the model predictions may be used with confidence.

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

2015 ◽  
Vol 19 (2) ◽  
pp. 839-853 ◽  
Author(s):  
P. Hamel ◽  
A. J. Guswa
Keyword(s):  
Land Use ◽  
North Carolina ◽  
Scale Model ◽  
Balance Model ◽  
Water Yield ◽  
Spatially Explicit ◽  
Model Predictions ◽  
Cape Fear ◽  
Annual Water

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.

scholarly journals A daily salt balance model for representing stream salinity generation process following land use change

2005 ◽  
Vol 2 (4) ◽  
pp. 1147-1183
Author(s):  
M. A. Bari ◽  
K. R. J. Smettem
Keyword(s):  
Land Use ◽  
Water Balance ◽  
Surface Runoff ◽  
Preferential Flow ◽  
Water Movement ◽  
Water Balance Model ◽  
Salt Flux ◽  
Balance Model ◽  
Generation Process ◽  
Salt Balance

Abstract. We developed a coupled salt and water balance model to represent the stream salinity generation process following land use changes. The conceptual model consists of three main components with five stores: (i) Dry, Wet and Subsurface Stores, (ii) saturated Groundwater Store and (iii) a transient Stream zone Store. The Dry and Wet Stores represent the salt and water movement in the unsaturated zone and also the near-stream dynamic saturated areas, responsible for the generation of salt flux associated with surface runoff and interflow. The unsaturated Subsurface Store represents the salt bulge and the salt fluxes. The Groundwater Store comes into play when the groundwater level is at or above the stream invert and quantifies the salt fluxes to the Stream zone Store. In the stream zone module, we consider a "free mixing" between the salt brought about by surface runoff, interflow and groundwater flow. Salt accumulation on the surface due to evaporation and its flushing by initial winter flow is also incorporated in the Stream zone Store. The salt balance model was calibrated sequentially following successful application of the water balance model. Initial salt stores were estimated from measured salt profile data. We incorporated two lumped parameters to represent the complex chemical processes like diffusion-dilution-dispersion and salt fluxes due to preferential flow. The model has performed very well in simulating stream salinity generation processes observed at Ernies and Lemon experimental catchments in south west of Western Australia. The simulated and observed stream salinity and salt loads compare very well throughout the study period. The model slightly over predicted annual stream salt load by 6.2% and 6.8%, with R2 of 0.95 and 0.96 for Ernies and Lemon catchment, respectively.

scholarly journals A daily water balance model for representing streamflow generation process following land use change

2005 ◽  
Vol 2 (3) ◽  
pp. 821-861
Author(s):  
M. A. Bari ◽  
K. R. J. Smettem
Keyword(s):  
Land Use ◽  
Soil Moisture ◽  
Land Use Change ◽  
Water Balance ◽  
Water Balance Model ◽  
Groundwater Depth ◽  
Balance Model ◽  
Streamflow Generation ◽  
Moisture Balance ◽  
Soil Moisture Balance

Abstract. A simple conceptual water balance model representing the streamflow generation processes on a daily time step following land use change is presented. The model consists of five stores: (i) Dry, Wet and Subsurface Stores for vertical and lateral water flow, (ii) a transient Stream zone Store (iii) a saturated Goundwater Store. The soil moisture balance in the top soil Dry and Wet Stores are the most important component of the model and characterize the dynamically varying saturated areas responsible for surface runoff, interflow and deep percolation. The Subsurface Store describes the unsaturated soil moisture balance, extraction of percolated water by vegetation and groundwater recharge. The Groundwater Store controls the baseflow to stream (if any) and the groundwater contribution to the stream zone saturated areas. The daily model was developed following a "downward approach" from an earlier monthly model and performed very well in simulating daily flow generation processes observed at Ernies (control) and Lemon (53% cleared) catchments in Western Australia. Most of the model parameters were incorporated a priori from catchment attributes such as surface slope, soil depth, porosity, stream length and initial groundwater depth, and some were calibrated by matching the observed and predicted hydrographs. The predicted groundwater depth, and streamflow volumes across all time steps from daily to monthly to annual were in close agreement with observations for both catchments.

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