Hydrologic Intervention

Hydrologic Overview

The Carman Valley watershed was identified as an impaired ecosystem as early as the 1950's.

The effects of human activity negatively affected the function of the alpine meadow as a sponge.  Both water quantity and timing were affected.  Additionally, the biology was impacted as well;  reduced vegetation resulted in less insect life, which in turn equaled a reduced population of birds and bats, waterfowl and songbirds, as well as amphibians, reptiles, fish and other wildlife.

The ponding and plugging has restored the hydrologic system in wetlands and riparian habitat for wildlife and aquatic species.  The recovered system will improve the water yield and quality and extend benefits to Central California water users.  The ponding and plugging has successfully healed eroded gullies into ponds for wildlife, fishery and amphibian use, and increased the water absorbing and holding capacity of the Valley.  The stream restoration has treated Knuthson and Three Cornered Meadows, the lower two of three strategically linked meadows in Carman Valley's series of cascading meadows.  These sites were identified by the TAC as the most active and problematic erosion sources.  In addition to ponding and plugging, the spillway at the bottom of Knuthson Meadow was improved and expanded, allowing it to handle a larger storm event than previously designed. 

Upstream from the spillway, the old railroad grades  - which previously diverted the meadows meandering channels – were recontoured so that the creeks found their previous (natural) hydrologic path.  Care was taken during this restoration to assure archeological sites and sensitive plants were not disturbed.  During construction, vegetation was stockpiled and later placed on the plugs to revegetate with on-site material.  The result was fantastic – the proof is in the monitoring that has occurred since construction:  more biologic activity, water storage and capacity has increased (even in 2002, a relatively dry year) and the water table, as measured with piezometers, has increased as well. Bird and bat activity has markedly increased, and there is hope that the willow flycatcher will make a full recovery in this restored system.

Knuthson Meadow AFTER

The results in Three Cornered Meadow are even more dramatic.  Check out the extreme downcutting in the pre-restoration photo and the resulting pond in the post-restoration photo.

Three Cornered Meadow BEFORE

The spillway at the bottom of Three Cornered Meadow was a challenge because of the steep gradient.  Large boulders were strategically placed in the previously downcut channel, and vegetated soil was placed in between the boulders.  The outlet was also reshaped to allow water to slowly release without erosive effects against the banks.

Three Cornered Meadow AFTER