Astudy that compared eight climate change scenarios to historic averages found that Ashland Creek flows would increase in spring but decrease in summer.

Astudy that compared eight climate change scenarios to historic averages found that Ashland Creek flows would increase in spring but decrease in summer.

Ashland, which relies mainly on Ashland Creek for its potable water, already faces summer water shortages in dry years. Shortages led to water curtailments in the summers of 2001 and 2009.

The climate change study looked at a range of temperature increases. For example, average temperatures in January could rise 0.54 degrees to 4.5 degrees. Average temperatures in July could rise 3.4 degrees to 10 degrees.

The climate change study by University of Washington Research Assistant Professor Alan Hamlet has important implications as city officials and the appointed Ashland Water Advisory Committee examine options for boosting the town's already limited water supplies.

"Climate change could affect our water supply dramatically," said Pieter Smeenk, a city of Ashland engineer tasked with helping the Water Advisory Committee. "It changes the timing of our supply. We'll have more supply, but earlier. It's going to be wetter in the late winter and spring."

Ashland Creek flows historically peak in mid-May and remain high until nearly the end of June before dropping off. Flows don't fall to extremely low levels of below 10 cubic feet per second until mid-August.

The average of the climate change scenarios predicts flows will be higher beginning in December and will still peak in mid-May. But flows will plummet to below 10 cubic feet per second in mid-July.

Added rain and earlier snowmelt in the late winter and spring could spell trouble for Ashland because Reeder Reservoir, which stores water above Lithia Park, has limited capacity to store higher creek flows that come then, Smeenk said.

"Reeder Reservoir fills up every year. It's not like irrigation district reservoirs. Those are oversized so they can take advantage of more water. If they get more water, they get to keep it. We have to spill it out," he said.

Reeder Reservoir gradually drains during the summer until fall rains return to replenish supplies.

Smeenk said faster snowmelt also could increase the risk of flooding, which could jeopardize the city's water treatment plant above Lithia Park.

A 1997 flood triggered a landslide that partially buried the water treatment plant's chlorine building. Surprisingly, it did little operational damage and the plant was working again shortly after flooding subsided, Smeenk said.

However, Ashland's water supply was turned off for about 11 days because of water and sewage pipe failures downstream, he said.

As part of creating a Water Conservation and Reuse Study and Comprehensive Water Master Plan for Ashland, the firm Carollo Engineers has prepared preliminary cost estimates for options that would make the water supply more stable and would increase supplies.

The firm will prepare more precise cost estimates as it continues its work, Ashland Public Works Director Mike Faught said.

Population growth will outstrip Ashland's current water supply in 2016, according to estimates made several years ago. The rate of population growth has slowed slightly since then, Smeenk said.

Finishing the Talent-Ashland-Phoenix water pipeline that brings extra Medford water to the south end of the valley would cost Ashland $12.7 million on top of $2.5 million Ashland already has spent. The pipeline now ends in Talent.

That option would provide additional water as well as a back-up potable water supply if Ashland's water treatment plant was not working.

Digging ground wells would cost $8 million to $16 million. A $1 million study to see whether the idea is feasible would be required first, according to Carollo Engineers' estimates.

The well option also boosts water supplies and provides back-up potable water.

Putting a Talent Irrigation District canal inside a pipe to stop leakage and evaporation — thus boosting the amount of water that reaches Ashland — would cost $20 million.

That provides more water, but not a back-up potable water supply if the water treatment plant is down. Irrigation water must be treated before it can be used for drinking water.

Spending $5.3 million to pipe Ashland's highly treated sewage effluent to large areas such as the Oak Knoll Public Golf Course for irrigation would lower demand on limited potable water supplies, but not provide back-up potable water.

Expanding and fortifying the water treatment plant at a cost of $5 million to $10 million would provide neither additional water nor a back-up potable water source, but it would strengthen the plant to withstand flooding.

Building another dam on a city-owned parcel high in the forested Ashland Watershed would cost $75 million and have environmental consequences. Ashland could store more water, but that water would still have to go through the treatment plant, according to Carollo Engineers.

Reach Ashland Daily Tidings reporter Vickie Aldous at 541-479-8199 or vlaldous@yahoo.com.