Hydroclimatic impacts of perennial biofuel crop expansion

Perennial biofuel crops (e.g. miscanthus and switchgrass) offer a potentially viable energy pathway that can increase U.S. energy independence and security while simultaneously mitigating greenhouse gas induced climate change. If planted on abandoned and degraded pastures and farmlands, recent research has indicated that such perennial biofuel crops could provide 26 – 55% of liquid fuel consumption. However, conversion of current landscapes to perennial biofuel crops could lead to unintended soil moisture and groundwater depletion via enhanced evapotranspiration (ET). Therefore, hydroclimate impacts (i.e. soil moisture, streamflow and groundwater depletion) must be further investigated to assess whether or not near-surface cooling, via the aforementioned ET pathway, is sustainable. This research evaluates the sensitivity of hydrological impacts to perennial biofuel expansion by conducting high resolution simulations with and without biofuel crop representation during an extreme drought year (2011) and a weak El Nino year (2007). Using continuous, triply nested simulations with a 2km grid spacing for the innermost domain, we utilize WRF/ARW (version 3.6) coupled to NOAH land surface model. Perennial biofuel crops are represented in suitable locations identified in Northeastern Oklahoma using ArcGIS 10.1, and representation of bioenergy crops is made by altering rooting depth, leaf area index, and albedo. Preliminary results indicate a localized cooling effect in areas of perennial biofuel crop expansion coincident with enhanced latent heat flux and depleted soil moisture. Our results also reveal a reduction in the urban heat island signature of Tulsa, Oklahoma, due to localized cooling associated with perennial biofuel crops. This alternative energy source could reduce a considerable fraction of anticipated warming attributable to greenhouse gas emissions for the regional scales analyzed, consistent with prior research, thereby serving as a dual adaptive and mitigation approach to climate change at local scales. This study serves as an initial step towards exploring the long-term sustainability of perennial biofuel expansion associated with extreme hydrological conditions aimed at highlighting mechanisms and processes linked with this energy pathway.