From Ditches to Wells: How East Greenacres Learned to Water a Growing Prairie

From Black Bay, the ground tells two stories. South of the neighborhood the Spokane River runs past the falls, and north of it the land flattens into the Rathdrum Prairie, the broad bench where Post Falls has done most of its growing. That growth needed water, and in 1921 local farmers formed the East Greenacres Irrigation District to supply it. Fields and farmland dominated the prairie then, crops of oats, barley and hay covered a sparsely populated landscape, and the new district's job was simply to keep those fields alive through the dry North Idaho summer.

The first system was humble and troublesome. The district pumped water from Twin Lakes, sending it down Rathdrum Creek into an open canal and lateral ditches. The Bureau of Reclamation records that the district first planned to irrigate about 3,000 acres and later reduced that to about 1,500 acres, and that the system it built was extremely expensive to maintain and suffered extremely high water losses. Drawing on Twin Lakes also made the lake itself rise and fall with the irrigation season, and lakeshore owners eventually challenged the district in court over the lake's operating levels.

The answer, worked out over the following years, was to leave the lake alone and tap the water under the prairie instead. At the request of Idaho legislators, the Bureau of Reclamation studied a redesign using groundwater from the Rathdrum Prairie Aquifer. Water users voted for the plan in February 1964, Congress authorized the rebuilt unit in 1970, and construction ran from 1972 to 1976. Crews built three deep well pumping complexes with fourteen pumps, a concrete regulating reservoir, and a buried pressure pipe system with 357 irrigation turnouts and 248 domestic turnouts. Pumping for irrigation and domestic use began on May 17, 1976, and the last construction was finished that December. With the lake no longer drawn down, Twin Lakes levels stabilized, and the district notes that tourism and recreation increased and fish and wildlife habitat improved.

Then the prairie itself changed around the pipes. Subdivisions and businesses steadily replaced the oat, barley and hay fields, and a farm water system quietly became city infrastructure. At its centennial in 2021 the district reported boundaries covering 7,333 acres, of which 5,340 acres are classified as irrigable, with fourteen wells in three complexes, 5,300 horsepower of pumping capacity able to deliver 58 million gallons a day, and 89 miles of pipelines. It served a population of about 9,889 people through nearly 4,000 domestic connections and 1,000 irrigation connections. Forty-five years earlier, it had fewer than 250 domestic connections. Its manager estimated that the district covers a quarter to a third of the city of Post Falls, and reporting in 2021 put new residential hookups at an average of 300 to 400 a year.

The district marked its centennial with a pointed reminder for a fast-growing city: when the topic of growth and water availability comes up, remember that East Greenacres served the prairie first as agriculture, with a higher water use, before residential development arrived. It is a fitting footnote to the growth of Post Falls. Long before the rooftops spread north from the river toward the prairie, farmers had already organized, argued over a lake, and rebuilt their water system once, and that century-old farm district still helps water the city that grew up around it.