Retention vs Detention Storage
When drought-weary observers of winter flood flows yearn for more storage capacity they are usually thinking of reservoirs retained by dams. But opportunities for detention storage are off most folks’ radar.
That needs to change, especially since the opportunities to expand/ restore detention storage are vast, in California and doubtless elsewhere. Humans have been unwittingly degrading watershed detention functions since our mastery of fire.
As defined in this site’s Glossary:
Detention: temporary storage of water. Below ground, soil water drainage by gravity is slowed, though not stopped, in macropores. In fact, macropores are among the primary conduits for “preferential flow” through the soil profile. Above ground, runoff is typically detained by snow, but may be slowed by other semipermeable means — most typically by routing through vegetation and soil, but other means are possible.