This project uses a model study system across the North Hilo-Hamakua Districts of Hawaii Island to model climate change and invasive species impacts on hydrological yield of 86 streams, and the potential response of yield to management including watershed restoration (invasive plant removal) and protection (fencing).
Across this system, total annual rainfall ranges from just under 2000mm per year to over 6000mm per year, but temperature, soils, and vegetation vary minimally. This project integrates hydrological modeling with spatial data on stream habitat condition (measured for the project area), critical habitat for plants and animals, ownership type and conservation status, cost of management, and management efficacy in order to create a watershed decision support tool (WDST). This tool will forecast: 1) climate change and invasive plant effects on stream flow; 2) threat management effects on stream flow; and 3) costs and hydrological benefits of management.
Rising sea levels are being caused by a change in the volume of the world's oceans due to temperature increase, deglaciation (uncovering of glaciated land because of melting of the glacier), and ice melt. This data viewer can provide a preliminary look at sea level rise and how it might affect coastal resources across the United States (with the exception of Alaska and Louisiana). Data and maps can be used at several scales to help gauge trends and prioritize actions for different scenarios.
This data viewer can provide a preliminary look at sea level rise and how it might affect coastal resources across the United States (with the exception of Alaska and Louisiana). Data and maps can be used at several scales to help gauge trends and prioritize actions for different scenarios.
Ten headwater catchments in the southern Sierra Nevada have been studied since 2003 with regard to climate conditions, water yield, and water quality. Five of the catchments are in the current rain-snow interface climate zone and five are in the snow-dominated zone. Since there is only a 1,000 foot difference between these zones, the higher elevation catchments are expected to transition to a combination of rain and snow as climate changes in California. Studying how the lower elevation area functions gives us insight about how the higher elevation area will function with a changing climate; for the southern Sierra Nevada this is predicted to be less snow and more rain with about the same total amount of precipitation. This knowledge is very important as 50% of the surface water for California originates in the Sierra Nevada.
What will the rivers of the Pacific Northwest look like in the future? Will they be stable or unstable? Will they have salmon or other species? Will the waters be cold and clear or warm and muddy? These questions motivate our study of the effects of climate warming on streams draining the Cascade Mountains.
Previous studies have shown that snowpacks throughout the Cascades are highly vulnerable to warming temperatures, readily changing from snow to rain, and melting earlier. Less certain is how these changes are likely to affect streamflows, particularly in streams that derive much of their flow from deep groundwater and springs. These groundwater streams, which are currently characterized by very stable bed, banks, and vegetation, are particularly sensitive to increasing peak flows in the winter. We want to know how changing snowpacks and increased peak flows are likely to affect these channels, potentially changing their suitability as habitat for threatened species such as bull trout and spring Chinook. Results from our work, which include field and modeling components, will be used to guide management decisions affecting these streams: how dams are operated, whether water suppliers need to worry about turbidity, and how we should manage riparian vegetation.
A key challenge for resource and land managers is predicting the consequences of climate warming on streamflow and water resources. Over the last century in the western US, significant reductions in snowpack and earlier snowmelt have led to an increase in the fraction of annual streamflow during winter, and a decline in the summer. This study explores the relative roles of snowpack accumulation and melt, and landscape characteristics or 'drainage efficiency', in influencing streamflow. An analysis of streamflow during 1950-2010 for 81 watersheds across the western US indicates that summer streamflows in watersheds that drain slowly from deep groundwater and receive precipitation as snow are most sensitive to climate warming. During the spring, however, watersheds that drain rapidly and receive precipitation as snow are most sensitive to climate warming. Our results indicate that not all trends in the western US are associated with changes in snowpack dynamics; we observe declining streamflow in late fall and winter in rain-dominated watersheds as well. These empirical findings have implications for how streamflow sensitivity to warming is interpreted across broad regions.
Changes in timing and magnitudes of streamflows under climate change pose significant risks to ecosystems, infrastructure, and overall availability of water for human use. We have developed a spatial analysis that predicts how both peak (winter) and low (summer) streamflows are likely to change in the future for Oregon and Washington. This set of spatial tools gives land managers a full toolbox with which to anticipate and plan for streamflow changes on forest lands.
Water stress represents a common mechanism for many of the primary disturbances affecting forests, and forest management needs to explicitly address the very large physiological demands that vegetation has for water. This study demonstrates how state-of-science ecohydrologic models can be used to explore how different management strategies might improve forest health.
Widespread threats to forests due to drought stress prompt re-thinking of priorities for water management on forest lands. In contrast to the widely held view that forest management should emphasize providing water for downstream uses, we argue that maintaining forest health in the face of environmental change may require focusing on the forests themselves and strategies to reduce their vulnerability to increasing water stress in the context of a changing climate. Management strategies would need to be tailored to specific landscapes but could include: a) thinning; 2) encouraging drought-tolerant species; 3) irrigation; and 4) strategies that make more water available to plants for transpiration. Hydrologic modeling reveals that specific management actions could reduce tree mortality due to drought stress. Adopting water conservation for vegetation as a priority for managing water on forest lands would represent a fundamental change in perspective and potentially involve tradeoffs with other downstream uses of water.
Restoring riparian forests on streams where historic land uses have created open meadows could reduce maximum stream temperatures by as much as 7o C relative to current conditions, even under a future climate when air temperatures are 4o C warmer than today.
Summer maximum stream temperatures are near thresholds of thermal tolerance for salmon and trout in many streams throughout the interior Columbia River Basin. Salmon and trout populations in many of these streams are severely depressed, resulting in efforts to restore stream and riparian habitat. Climate change raises serious questions about the long-term outcomes of restoration because projected warming could make many of these streams and rivers uninhabitable for salmon and trout within a few decades.
We used the mechanistic stream temperature model, HeatSource, to examine future changes in stream temperature on the upper Middle Fork John Day River. Our model scenarios examined: 1) a +4 oC increase in air temperature; 2) ±30% changes in stream discharge from both changes in irrigation withdrawals and climate-change related loss of winter snowpacks; and 3) four riparian vegetation scenarios: 3a) current conditions where effective stream shade averages 19%; 3b) a post-wild fire scenario with maximum vegetation height of 1 m and 10% canopy density resulting in 7% effective stream shade; 3c) an intermediate condition representing a young-open forest or tall-shrub dominated vegetation with trees or shrubs 10-m tall and with 30% canopy density resulting in 34% effective shade; and 3d) a restored riparian forest with trees 30-m high and canopy density of 50% resulting in 79% effective stream shade.
Our model results showed the composition and structure of riparian vegetation were the single biggest factor determining future stream temperatures. In contrast, changing air temperature or stream discharge had relatively small influence on future stream temperatures. The post-wildfire and the current-vegetation scenarios were warmer than today, but in both cases, effective shade was low, so the stream was sensitive to air temperature increases due to climate change. The intermediate restoration, simulating a young-open forest or a tall-shrub dominated riparian zone, was slightly cooler than today. The biggest change resulted from restoring the riparian forest which decreased summer maximum temperatures by ~ 7 oC.
Stream data are needed to enable managers to understand baseline conditions, historic trends, and potential impacts of climate change on stream temperature and flow, and in turn on aquatic species in freshwater ecosystems.
NorEaST is being developed to provide a coordinated, multi-agency regional web portal to compile, store, map, and distribute continuous stream temperature locations and data across the Northeastern U.S.