Wednesday, January 26, 2022 The Nugget Newspaper, Sisters, Oregon WATER: Region9s geology plays a big role Continued from page 1 outside the city limits rely on their own individual or shared wells for their water. All wells are accessing groundwater. Groundwater vs. surface water Groundwater is the water that collects or flows beneath the earth9s surface, filling the porous spaces in soil, sedi- ment, and rocks. It originates from rain and melting snow and ice and is the source of water for aquifers, springs, and wells. The water table is an u n d e rg r o u n d b o u n d a r y between the soil surface and the area where groundwater fully saturates spaces between sediments and cracks in rocks. The saturated zone is bounded at the bottom by impenetrable rock or sediment. The aquifer from which the City of Sisters draws its water is a basalt aquifer. Surface water is the water that is available above ground in the form of rivers, streams, oceans, lakes, and wetlands. Surface water is mainly col- lected from precipitation. However, in the Deschutes River Basin, studies have determined there is a hydrau- lic connection (operated by the pressure of water) between groundwater and surface water. Groundwater appropri- ations (wells) have the poten- tial for substantial interference with surface water and could measurably reduce waterway flows. Likewise, low stream flows could reduce the amount of groundwater available to be pumped from a well. What is an aquifer? Aquifers are often iden- tified by the way they were formed. Alluvial aquifers are water-deposited (usually by moving water), and glacial drift aquifers are deposited by the gradual movement of gla- ciers. Large aquifer systems may be composed of several geologic formations, includ- ing both alluvial and glacial drift deposits. Coarse sand and gravel, transported and deposited by rapidly moving water, turns into permeable aquifer depos- its when buried. They can extend laterally from a few feet to many miles and can be paper thin to hundreds of feet thick. The Deschutes Basin aqui- fer has been described as a large bowl, with a deep end near the Cascade Mountains (and Sisters) becoming shal- lower up to the northeast and Madras. Much of the eastern side of the Cascade Range drains into this bowl, which is lined by large areas of perme- able volcanic rock. When the large annual precipitation at higher elevations collects on that permeable rock, the result is a substantial regional aqui- fer system and a stream sys- tem that is heavily dominated by groundwater, with either resulting springs when the groundwater is high or lower water levels when the ground- water level is lower. The headwaters of the Metolius and Fall Rivers, as well as the springs downriver that feed the Metolius, are examples of that groundwater being released. When it comes to water, Sisters is ideally located. Groundwater elevations are highest near the Cascade Mountains in the west and Newberry Volcano in the south and decrease to the northeast and north toward the confluence of the Deschutes and Crooked Rivers. The City only needs to drill down about 300-plus feet to reach copious groundwater. Surface water became the source for irrigation by the early farmers and ranchers in Sisters Country and beyond. A large network of open canals carried water through- out the area. Gradually, over the years, a number of those canals have been replaced by wells and irrigation ponds. In recent years, the Basin to the south irrigation districts central down by have been piping Sunriver. Some the remaining scientists believe canals to stop that the fault leakage into the could be respon- ground. sible for disrupt- For almost ing an even flow 100 years, due of groundwater to those leaky to the east from canals, the entire higher western area had an artifi- elevations. cially high water Long-term table. With the groundwater piping, the water level records in table is returning the central part to its original nat- of the Upper ural level, which Deschutes Basin is leaving some have shown that shallow wells dry, some areas are intermittently or experiencing per- MODIFIED FROM LITE AND GANNETT, 2002 permanently. Sisters lies at an advantageous spot over the region’s water table. sistent groundwa- Increasing ter level declines, water demands Some of the more recent particularly in an area extend- The demands for water in modeling done in the Upper ing from the vicinity of the region are coming from all Deschutes Basin, in coop- Bend, north toward Lake corners 4 a rapidly increasing eration with the Oregon Billy Chinook, and northeast regional population, agricul- Water Resources Department toward Redmond and Powell ture, environmental projects, (OWRD), explores the influ- Butte. The Deschutes Basin hydroelectric, businesses, and ence of well location and geo- Groundwater Mitigation recreation. Additional appro- logic structure on stream cap- Program allows for limited, priations for surface water ture by pumping wells. The additional groundwater devel- have been closed. In a col- OWRD report states: opment using mitigation to laborative effort, a new water