Fine-Resolution, Regional-Scale Terrestrial Hydrologic Fluxes Simulated with the Integrated Landscape Hydrology Model (ILHM) David W Hyndman Anthony D Kendall

Unprecedented Changes Pijanowski (Purdue) Land Use Change IPCC AR4 Climate Change Land Use Intensification USCB and USDA

Integrated Landscape Hydrology Model (ILHM) –Integrates 4 domains of hydrologic modeling –Intended for large-scale, fine-resolution simulations –Modular code, readily expandable –Readily incorporates GIS, remote sensing inputs

Muskegon River Watershed, MI –~7400 km 2 –Climate & ecological gradients Lake effect precipitation Deciduous/Mixed transition –Major historical land use change Forest  Agriculture Agriculture  Forest and Urban

Expanded Model Domain –~19,000 km to 400m grid cells –28-year simulation 1980 – 2007 Hourly timesteps

Select Input Data Types –GIS Inputs Land use Soil texture Subsurface geologic maps Elevation map –Gage climate data Precipitation Solar radiation Windspeed Relative humidity Air/soil temperatures –Distributed remotely sensed inputs NEXRAD precipitation Satellite Leaf Area Index (LAI)

Uncalibrated Streamflow Predictions –Baseflows well simulated, regardless of scale – some regional bias –Total discharge error less than 6% of annual precipitation 43 sq. km 629 sq. km 3711 sq. km

ET and Recharge Averages (1980 – 2007) –Highly spatially variable Soils, land use, climate variability –Recharge strongly sensitive to lake-effect precipitation

Monthly Watershed-Average Fluxes –2 annual recharge pulses: snowmelt/spring & early fall –ET dominates during the growing season –Storage in snowpack and soil are important to dynamics

Preliminary Climate Change Scenarios –Average of 24 GCM outputs A1B, A2, & B1 scenarios –Offset observed data using modeled anomalies

Changes to Groundwater Recharge –Average –More frequent snowmelt in all scenarios Smaller persistent snowpack Reduced spring recharge –Less fall recharge

Climate Change Implications –Higher spring water tables –More frequent spring floods –More seasonal wetlands –Earlier decline of summer water table –Lower summer baseflows –Longer low-flow period

Summary –Good predictions without site-specific calibration –Variability is the rule: Groundwater recharge typically treated as a static input in groundwater models Strong spatial and temporal variability at all scales Even 425 m resolution here not sufficient to fully describe land use and soils –Gradients in precipitation and temperature well below typical climate model resolutions Lake effect not well described by climate models