A range of human impacts led to the decline of habitat in Gold Creek. Historic clear-cut logging in the valley, including the large trees lining the channel banks, resulted in dramatic channel widening. The wider channel causes two problems: 1) Water spreads out over a larger surface, which decreases the creek’s depth and 2) Water infiltrates below ground – moves from above to below the streambed. Both of these factors contribute to more frequent dewatering (a period of time when the stream goes dry) occurring over longer sections of the channel.
In addition, the groundwater table has been signficiantly altered over time. Historically, Gold Creek Valley has been the site of many gravel pits providing materials for highway construction and expansion, but most of these pits were allowed to return back to their previous state as wetlands. However, this was not the case with what became Gold Creek Pond. To expand I-90 in the 70s and 80s, the Washington Department of Transportation (WSDOT) needed large quantities of gravel. About three quarters of a million cubic yards of gravel were extracted from the Gold Creek Pond pit. The shape of the pit and the elevation of its downstream outlet lowered the groundwater table across Gold Creek valley.
Because the pond is lower than the creek, it acts as a siphon, pulling water from the creek to the pond. This further exacerbates the dewatering effects on the creek. You can see this firsthand walking along the north shore of the pond. Even during the dry summer months, groundwater flows from the bank along the northern edge of the pond.
In addition to altering the groundwater table, the pond also has other negative effects. WSDOT built a levee to separate the creek from the gravel pit to keep water from entering the work site. That levee still exists today and keeps the creek disconnected from almost 90% of its floodplain. Furthermore, water in Gold Creek Pond heats up signficantly during the summer, which can reach leathal temperatures for bull trout and other fish species.
In totality, timber harvets, mining and development have created poor habitat conditions and contributed to dewatering of Gold Creek. These activities removed large wood from the system, which are vital for providing the shelter and stream complexity bull trout need to survive. And, they influence dewatering, which kills young bull trout rearing in the creek, and inhibits adult migration to spawn upstream in late summer/early fall. These are critical factors for populations that are already struggling and as a result, we continue to see bull trout numbers decline.