Percival Creek is an urban lake-fed creek discharging into Capitol Lake/Deschutes River. The headwaters are at Trosper Lake. At approximately 1 mile above its mouth, Percival Creek is joined by Black Lake Ditch, a man-made drainage channel built in 1922 originating at Black Lake. Black Lake Ditch accounts for nearly two-thirds of the total flow of Percival Creek below the confluence. A Burlington Northern railroad line parallels the creek in the lower reaches and a portion of Black Lake Ditch. Regional stormwater facilities treat significant amounts stormwater runoff from the heavily urbanized portions of the basin, but runoff remains a difficult challenge to mitigate, creating pockets of scour in the sand-dominant system. The City of Olympia rated Percival Creek as an "impacted" stream, where there is still some potential for properly functioning fish habitat that warrants a moderate level of protection and restoration activity.

Adult access is limited at the mouth by a WDFW managed fish gate, which directs hatchery Chinook to the hatchery facility at Deschutes River falls until sufficient eggs are collected. No species can utilize the creek until the WDFW-operated gates are opened. The City of Olympia is discussing options for gate management with WDFW, a proposal that will allow fish access to habitat in Percival Creek before the gate becomes open in the fall. The replacement of culverts at RW Johnson Road on Black Lake Ditch and Chaparral Road on Percival Creek corrected previous limitations for adult and juvenile passage. The installation of two fish ladders (at Mottman Road and below Highway 101) on Percival Creek corrected previous limitations for adult access.

The predominant land uses surrounding Black Lake Ditch is industrial and open space. Upstream of the confluence, Percival Creek has open space and residential development. Below the confluence, several land uses including commercial and mixed residential development are present. Development pressures have been significant during the past few decades. Thurston County, City of Olympia, and Tumwater own most of the riparian corridor of Black Lake Ditch and Percival Creek. The City of Olympia uses Black Lake Meadows, a large constructed wetland complex adjacent to the Ditch, to treat stormwater.

Description from the Salmon Habitat Protection and Restoration Plan for Water Resource Inventory Area 13, Deschutes. For more information see the previously stated document or the Salmon Habitat Limiting Factors Final Report Water Resource Inventory Area 13