(The following article recently appeared in the USGS EROS Center’s online forum called “Around the Center.” It was modified to highlight the work of Innovate Scientist Matt Schauer.)
In the upper Klamath River Basin of southern Oregon, Innovate scientist Matt Schauer and his colleagues at the Earth Resources Observation and Science (EROS) Center are working to help solve this complex water use question: When it comes to water, when does less really mean more?
The answer is important to various interests across the basin, where drought in recent years has resulted in insufficient water for agriculture and aquatic life, especially fish listed as endangered. One of the keys to managing the water resources is understanding not only how much water flows into Upper Klamath Lake, but how management of water resources in streams affects flow into that lake as well.
Upper Klamath is an important body of water for many reasons. It’s home to endangered suckers. It also is the source of water for irrigation on the Bureau of Reclamation’s Klamath Project. Droughts in recent years have forced regulators to reduce or stop irrigation withdrawals from streams that flow into the lake, giving rise to the question: How much water then is flowing into Upper Klamath Lake from the reduction in irrigation?
This is where Schauer and his colleagues come in. Schauer is part of a team that uses remotely sensed data scaled to Landsat 30-meter resolution and energy-balance principles to model the rates of evaporation and transpiration on fields in the upper basin. Energy balance involves an understanding that plants regulate their tissue temperatures by balancing energy inputs and outputs. As water and nutrients are transported from the soil to the plant’s leaves, evapotranspiration (ET) plays a major role in regulating leaf temperature through evaporative cooling, which requires conducting an energy balance between incoming sunlight and outgoing evaporation.
Important to Schauer’s work is the knowledge that through expended energy, a fully transpiring vegetated area can appear up to 40 degrees Fahrenheit cooler than bare areas with little evaporation. When used in combination with local weather datasets for irrigated lands, Schauer’s model can provide increasingly accurate and repeatable estimates of actual ET—the amount of combined water that either evaporates from the soil and vegetation surfaces, or is transpired by plants.
The amount of ET then is a measure of how much irrigated water is being consumed by crops in this arid basin. Figuring out how much water flows into Upper Klamath Lake from the reduction in irrigation simply requires taking ET during a year when irrigation is reduced and comparing it with a year when there is normal irrigation.
Using independent satellite data from space for their ET maps, Schauer and his group started working on the Klamath Basin issue in 2017 with funding from the Bureau of Reclamation. To begin with, they tapped into Landsat’s rich archive to produce ET maps from 2004 and 2006—representing a dry year and a wet year back when much less water regulation was occurring. Then they averaged the two to arrive at a baseline for comparing water usage in each of 2013, 2014, 2015, and 2016, when more significant water management occurred.
While 2013 showed significant decreases in water consumption and irrigation along the tributaries upstream from Upper Klamath Lake, other years weren’t so definitive.
The USGS Oregon Water Science Center office has attempted other methods for measuring water consumption in the upper basin. For example, it also looked at stream flow in years with reduced irrigation and tried to compare it with years of normal irrigation.
For now, Schauer’s work has been beneficial on year-to-year comparisons. However, parties involved in the upper basin would like to see those findings get to a monthly, or even weekly, measurement of water use. Perhaps they will get there some day, however, the USGS Oregon Science Center likes the option and the product they are getting out of Innovate staff at USGS EROS.