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<div style='text-align:Left;'><div><div><p style='margin:0 0 0 0;'><span style='font-size:12pt'>The CETWI model improves the conventional TWI by incorporating the USGS DEM Curvature, Slope, and Solar insolation, and PRISM precipitation and vapor pressure create the CETWI model. In addition, the “Hydrologic Influence” and “Depressions” are post processed derivatives created by Teren, Inc. The CETWI value, scaled with zero beginning the lowest potential for moisture to accumulate to higher values being the highest potential for moisture to accumulate, uses six derivatives (Climate, Curvature, Depressions, Hydrologic Influence, Slope, Solar). For example, in the northern hemisphere, more northerly aspects will have higher values, while more southerly aspects will have lower CETWI values. However, northerly (cool) aspects with greater evapotranspiration losses than neighboring cool aspects will have a lower value, and southerly (hot) aspects with lesser evapotranspiration losses than neighboring hot aspects will have a higher value. The importance of using climate-enhancement enables the CETWI model to capture similar terrain properties but assigning them different index values to each based on the relative precipitation amount. The model allows for averaging the terrain variables into a weighted raster that reflects local hydrological processes influencing broad scale hydrology and climate patterns (a process that standard TWI does not provide). The hydrology model used in CETWI relies on a D-infinity conceptual model that routes hydrology down slope based on the probabilities of directed flow. This captures the accumulated hydrologic processes that spread out through space if the terrain is flat and wide or confines flow in confined flow paths. The climate stratum controls how a given hydrology flow path gains energy or loses energy based on accumulated effective precipitation and slope. This results in hydrology that will gain as accumulated relative precipitation increases, and accumulated slope is steep, but will lose “energy” as the slope approaches zero. This surface is continuous for all hillslopes, which means that it captures localized hillslope hydrological processes that influence potential productivity and soil forming factors. CETWI performs well in flat to sloping landscapes.</span></p><p><p style='margin:0 0 0 0;'><span /></p><p style='margin:0 0 0 0;'><span /></p><p style='margin:0 0 0 0;'><span style='font-weight:bold;font-size:12pt'>Purpose: </span><span style='font-size:12pt'>The Climate-Enhanced Topographic Wetness Index (CETWI) is a climate and terrain driven deterministic model using a suite of derivatives to estimate effective soil surface moisture from precipitation and inflow across a continuous earth surface. Climate enhancement captures “effective precipitation”, which is the amount of precipitation minus the amount of evaporation. The CETWI model identifies water movement and can inform land managers for conservation, management, and engineering practice solutions. The CETWI pixel values aid in the prediction of subtle differences in ecological sites or soils impacted by water movement across the landscape that will assist the conversation between the landowner and the conservation planner. The CETWI pixel values aid in process-based modeling efforts to determine areas that will respond similarly to conservation practice implementation. They can help identify potential movement of nitrates and chemicals in soils, thus aiding in conservation planning. NRCS creates many defined policy areas and geographic boundaries where CETWI values can aid in defining or documenting these boundary areas. USDA-NRCS, CEAP-Grazing Lands, with expertise from outside contractors, namely Teren Inc. and Prairie Hills Soils Consulting LLC., collaborated in the creation of the CETWI model. </span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Creation Date:</span><span> 20240507</span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Publication Date: </span><span>20240507</span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Revision Date: </span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Refresh Cycle: </span><span>Updated periodically as new imagery becomes available</span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Version: </span><span>1.0.0</span></p><p style='font-size:12pt'><span style='font-weight:bold;'>Change Log: </span><span>Service Deployed</span></p><p style='font-size:12pt'><a href='mailto:usdafpacbc@servicenowservices.com?Subject=GEOSRV' target='_blank' style='text-decoration:underline;'><span style='font-weight:bold;'>Report Service Errors</span></a></p><p><span /></p></div></div></div> |