Conceptual models for surface water and groundwater interactions at pond and plug restored meadows

Abstract

The pond and plug meadow restoration method, used for incised meadows in the Sierra Nevada Range, takes available alluvium on site to dam the incised channel in several places. Groundwater storage gained from restoration may alter flow paths and surface water availability. Water flowing through the meadow is elevated, usually to an alternate channel, and slowed by floodplain spreading, meanders, and vegetation roughness. Each dam, or plug, creates a pond, filled as the water table rises closer to the meadow surface. Expanded riparian vegetation and slowed water movement increase evapotranspiration (ET) following restoration. Landsat derived Normalized Difference Vegetation Index (NDVI) increased by 0.07 (p <0.001) on 30 of 31 meadows. Conceptually a meadow may act as (1) a sponge, storing abundant water from snowmelt or precipitation and releasing water in dry periods; (2) a valve, regulating water outflow from springs recharging the meadow, and/or (3) a drain, allowing water from the meadow to percolate into a regional aquifer. Areas in eight northern California meadows were classified into one or more of these conceptual models using ET, summer pond and groundwater elevations, stream gauges, and climate data. Evaporation from open pond water was 20% to 80% of their summer decline (−0.11 to 1.78 m [−0.36 to 5.84 ft]) and 1% to 7% of total meadow ET. Meadow ET estimates ranged from 0.32 to 0.40 m (1.05 to 1.31 ft). Water from springs captured by historic channel incision can be redirected from discharge to meadow restoration and ET. This study was conducted in a dry period and the data reflect effects of below average precipitation.