1. Centre for Ecology & Hydrology, Wallingford OX10 8BB, U.K.
2. Department of Crop, Soil & Environmental Sciences, Division of Agriculture, University of Arkansas, Fayetteville, Arkansas 72701, United States
3. Department
of Geosciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
4. Centre for Ecology & Hydrology, Lancaster LA1 4YQ, U.K.
5. Arkansas
Water Resources Center, University of Arkansas, Fayetteville, Arkansas 72701, United States