| Popis: |
Estimation of runoff from windrow compost pads is a challenge due to the different hydrologic properties of the compost pad and moisture storage in the compost, both of which change with time. The surface of a compost pad is usually crushed rock on top of a compacted layer of clay and may contain a thin covering of washed compost over the gravel along with the mounds of compost extending above the surface. The curve number method is popular for evaluating runoff from rainfall, but because the porous aggregate promotes greater infiltration and drainage, a new approach was considered. Four curve number based methods are assessed for accuracy in estimating runoff on a windrow compost pad using 16 storm events occurring on a 7284 m2 composting facility in Athens, Georgia. The methods include (1) a tabulated effective curve number, (2) a dynamic curve number based on the magnitude of the rainfall, antecedent rainfall, and areal coverage of the compost piles, (3) an asymptotic curve number, and (4) an event-based optimized curve number. Using the NRCS effective curve number consistently under estimated event runoff (r2 = 0.92). Using a dynamic curve number improved the runoff estimation (r2 = 0.98). The asymptotic curve number method performed comparable to the effective CN method (r2 = 0.90) while the event based optimization process only slightly improved over the curve numbers selected from the standard NRCS tables (r2 = 0.92). |
