The Sierra Nevada provides about 40% of the runoff for the whole state of California, and a much larger component for specific basins, including those draining into Nevada. The range serves water to over 10% of the U.S. population. The Sierra Nevada ecosystem has been described as teetering on the edge because of its summer aridity, encroaching development and air pollution. Snowmelt and streamflow timing are advancing earlier each spring in response to general warming (as much as +2ºC in recent decades). This seasonal shift implies increased risk of floods in springtime, and droughts and wildfires in late summer. These changes are not unique to the Sierra Nevada . The changing water balance and water distribution patterns, in both space and time, will radically impact ecosystems and water supplies in the Sierra Nevada and other western mountains in coming decades. Yet the knowledge base for implementing sound hydrologic management in Western mountains is notably weak. Information about water demand is not easily accessible. The effectiveness of various water and land-management practices and restoration techniques are largely untested. Forecasting tools lack the measurement base to make major advances.
Using a nested design, the proposed observatory will provide both extensive data for studies at the largest scales, and intensive measurements and facilities for process studies at the smaller scales. In terms of new ground-based facilities, the planning group concluded that the distinctive hydrologic opportunity in the region was a mountain-range-scale research program exploring the hydrology of snowmelt-dominated systems, which control much of the Wests water supply. It is recognized that there are already significant investments in hydrologic research below the mountain front (e.g. riparian system processes, sedimentation, salinity, water quality, groundwater-surface water interactions); many of these research initiatives extend only into the foothills, owing to the difficulties of hydrologic research in mountainous regions. The greatest knowledge gaps are in mountain hydrology. Water resource management in the lowlands is impaired primarily by our limited understanding of the hydrologic processes above the mountain front..
The underlying design of the proposed observatory is based on a mountain range, but also has a strong basin focus. In the Sierra Nevada and other mountain ranges, there are multiple umbrella mountain-range-scale issues that are important in themselves, which cannot be investigated at the scale of a single sub-basin. It must also be recognized that most ~10 3km 2sub-basin making up the Sierra Nevada are discnnected from the valleys by foothill dams and reservoirs, which are operated as a system. The range-scale issues link with other issues down at the sub-basin, headwater-catchment, plot and smaller scale - understanding is needed at multiple scales in this chain.
Why this range?
Why the Sierra Nevada and not another range? Scientifically, the Sierra Nevada offers opportunity to study essentially all of the questions that have been discussed by the planning group thus far. Logistically, it offers the possibility to leverage millions of dollars of research and infrastructure from other agencies, and offers the best access of any mountain range in the west. The Sierra Nevada is big, scientifically interesting in many ways, tractable, subject to technological breakthroughs and desperately important to the entire Western U.S.
Sierra Nevada Hydrologic Observatory