Dramatic rocky peaks, rolling green mountains, and dozens of rivers make the Pacific Northwest a year-round playground for outdoor enthusiasts. These enjoyable nature spots offer more than recreation opportunities. They are the water source for residents, wildlife, agriculture, and industry.
We often take for granted that water is available at our fingertips, but it’s fascinating to pause and think about how that water is making its way across the land, through waterways, and into our homes. Understanding the availability and movement of water is important – especially in an era marked by extreme environmental change.
The journey water takes from its source to our faucet is unique for each community.
Water from the Tualatin River takes a journey unlike most in the region. In many places in the western United States, snowpack is a critical water source. Snowpack is snow that stays frozen for many months of the year. With each new snowfall, the snowpack gets deeper and stores more water. When temperatures rise above freezing, water is released slowly, beginning at the top layer. The gradual melting of snow is especially important for areas that have a dry season, like California’s Central Valley.
In Portland, when people cool off on a hot summer day by taking a dip in the Willamette River, they’re swimming in gallons of snowmelt originating in the Cascade Mountains. If these mountains weren’t covered in snow most of the year, the rivers and streams would run dry when we need them the most.
Rainfall is the primary water source for the Tualatin River.
The Tualatin River begins in the Coast Range Mountains. Unlike the Cascade Mountains, which are nestled hundreds of miles inland and incredibly tall (averaging more than 14,000 feet above sea level), the Coast Range Mountains hug the Pacific Ocean and have an average height of 1,500 feet. These characteristics create big differences in climate! Instead of snow, the Coast Range mostly receives rain in the winter. Any snow that arrives won’t hang around long enough to become snowpack. Rainfall as the primary water source presents both benefits and challenges for land managers in Washington County.
A benefit of having rain as a primary water source is the ability to plan ahead.
Scientists make strong predictions about when, where, and how much rain will be delivered. The need for large amounts of water during the dry summer has resulted in the creation of reservoirs like Hagg Lake. During the winter, resource managers collect and save water in reservoirs to be used later. Managing water use and distribution across communities is becoming more important as our communities grow larger and urban development continues. Expected population growth in the region has already sparked discussion of building other reservoirs to meet the needs of a more crowded Washington County.
An additional complication for resource managers is climate change. A warming climate presents challenges to predicting rainwater and snowpack accumulation. Already, scientists are noticing changes in when, where, and how much snow and rain is delivered each winter. This can create big problems for communities that don’t have methods for saving snowmelt or infrastructure that can direct large flows of rain.
An enormous amount of snow is typically greeted with joy – grab those skis, it’s a snow day! But large amounts of rain? Not so much. In urban environments, impervious surfacesImpervious Surfaces Surfaces that water can’t pass through., like sidewalks and roads, don’t allow water to soak into the ground. Instead, rain runs off horizontally, looking for a path into the ground or the nearest stream. Too much rain can overwhelm infrastructure like water treatment plants, sewers, and reservoirs. With nothing standing in its way and nowhere to go, rainwater can become strong enough to damage property, cause landslides, and spread pollution far and wide. The same can be true for snowpack that melts too quickly – instead of a gradual release of water, snowmelt can rapidly become a powerful flow of water. But there are many ways that communities can better manage rainwater.