Ebey's Prairie The Ebey’s Prairie watershed is located in the central portion of Whidbey Island, Washington. The approximate boundary of the watershed is shown on the Ebey's Watershed Map. The watershed is approximately 2,200 acres in size and is comprised of a mix of land uses including farms and forest lands, residences, businesses, a portion of the Town of Coupeville, Whidbey General Hospital, and public schools. This watershed drains south into Admiralty Inlet, a marine water body designated by Washington State as 'Extraordinary' for protection of aquatic life uses (WAC 173-201A-612). Recreational shellfish harvesting areas are located both east and west of the watershed’s outfall location.
Land Uses Ebey’s Prairie consists primarily of agricultural lands (1,653 acres, or approximately 75%). An additional 237 acres (11%) lie within the Town of Coupeville and approximately 314 acres (14%) are in forest and/or low-density residential. Like most of Whidbey Island, Ebey’s Prairie depends on an EPA-designated sole source aquifer for its water supplies.
Historically, the majority of acreage in the watershed has been used for agriculture since European settlement in the mid-1800’s. Early crops included potatoes, wheat, barley, oats, and hay, as well as sheep, pigs, and dairy and beef cattle. Poultry farms were common in the watershed, many raising turkeys and chickens on pasture. Current crops include barley, seed peas, seed cabbage, winter squash, and alfalfa/ grass hay, Livestock farms predominantly raise beef cattle and dairy replacement heifers. While historically dairy production has been a significant part of the agricultural production of the watershed, there currently is no dairy production with milking cows.
Geology & Soils Geologic evidence indicates that Ebey’s Prairie was submerged beneath glaciers and marine waters at the end of the last ice age and has rebounded in elevation as the land was relieved of the weight of the glaciers. Most of the watershed is underlain by glacio-marine sediments that were deposited near the glacial terminus at the end of the Pleistocene, about 11,000 years ago. Currently, the watershed consists of very deep glacial sediments, with a variety of distinct features exposed at the surface, including outwash deltas, kettles, and relic marine shorelines. These features have formed a watershed that is fairly broad with mostly gentle slopes. The most significant slopes occur along the west edge, in the vicinity of Sherman and Cemetery Roads, and just above the shoreline near the watershed’s outfall at Ebey’s Landing.
Soils are variable in the watershed, ranging from wet muck to hydric loam to deep, well-drained fine sands. The areas of hydric soils generally follow the drainage patterns of the watershed. The attached Hydric Soils Map shows the regions of ‘All Hydric’ soils extending from near the outfall in a northeasterly direction, then splitting into two lobes near the center of the watershed. These lobes of hydric soils mirror the surface and subsurface drainage pathways from the northwestern and northeastern portions of the watershed, and are indicative of wetter conditions in the past, before drainage infrastructure was installed.
The southwesterly portion of the watershed is characterized by deep deposits of fine, wind driven sands. As a result, this area has better drainage in the upper soil profile than other parts of the watershed, exhibiting little or no seasonally saturated conditions.
Climate Rainfall averages only about 21 inches annually, due to the ‘rain shadow’ effect of the Olympic Mountains located to the southwest across Admiralty Inlet. Precipitation is seasonal, with the majority falling between October and April, while little to no precipitation occurs during the summer. Concurrently, these seasonal variations in precipitation result in little to no surface water flows in the watershed during the summer.
History of Ebey’s Prairie Drainage System Prior to European settlement, the Ebey’s Prairie watershed had more complex hydrologic characteristics than currently exists. Historically, the prairie included significant wetland areas and experienced more extensive seasonal ponding and saturated soil conditions. In the middle of the twentieth century, an elaborate network of ditches and subsurface drain tiles was installed to drain the soils for agricultural uses. This drainage system has resulted in a significant reduction in the amount of area that becomes saturated or inundated seasonally, making much of the watershed suitable for agriculture.
copyright 2017 Whidbey Island Conservation District - PO Box 490, Coupeville, WA 98239 360-678-4708 888-678-4922