Hydrogeologic Investigation of the Klamath Marsh, Klamath County, Oregon

Application of a Novel Groundwater Storage Analysis Tool to Assess Drought Impacts in a Groundwater-Driven Basin in the Klamath Watershed, Oregon, USA

“…Uncoupled from a conventional rain-runoff relationship, the actual headwaters of the Williamson River are at the Klamath Marsh. Isotropic analysis performed my Melady (2002), and Cummings (2007) confirmed distinct differences in thein deuterium and oxygen isotope ratios in the surface and groundwater, along with distinguishable concentrations of magnesium, calcium, potassium, and sodium. [1,6].…”

“…The river then turns south flowing into the Klamath Marsh in the center of the basin (Figure 2). In the marsh it flows through various irrigation canals, restored streambeds, and culverts before it sheet flows across the marsh is dissipated by high levels of evapotranspiration and groundwater infiltration [1,2,[5][6][7]. Exiting the marsh, the water is replenished/replaced by seeps and springs fed by groundwater with origins in the Cascades to the west of the basin.…”

“…Mount Mazama is the high point of the basin at 8,157 ft (2,486 m), which then slopes downward to 4090 ft (1245 m) in elevation at the Klamath Marsh. A simplified geology of the basin subdivides the lithology into three major geological units: 1) the surficial pumice blanket; 2) intertwined beds of sand, clay, gravel, pyroclastics and basalt (Yonna formation); and 3) the underlying andesitic/basaltic bedrock which is the main water bearing unit [1,3,[5][6][7][8]. On the surface, pyroclastic-fall pumice, ash and other volcaniclastics from Mt.…”

“…The Cascade mountains (including Mount Mazama) receive upward of 60 in (150 cm) of precipitation per year, mostly as snow. The central and eastern portions, in the rain shadow, receive as little as 18 in (45 cm) of precipitation per year [1,5]. Temps range from highs of 40 °C to lows of -31 °C.…”

“…Beginning in 2001, there has been an overall trend in the decreasing volume of water leaving the basin as surface flow. Prior to 2000, stream flow leaving this basin as measured at a United States Geological Survey (USGS) gage could be roughly correlated with the mountain snowpack from the previous 2 to 3 years [1][2][3]. Since the turn of the millennia, climate change, drought, and supplemental groundwater use have as-yet unquantified impacts to the aquifer [4] potentially disrupting a previously balanced hydrologic system.…”