A Framework for Describing the Hydrologic Regime of Lakes for Improved Water Quantity Management
Image credit: AGUAbstract
All lakes naturally experience water level fluctuations and it is well-understood that the amplitude and pattern of these fluctuations play a critical role in lake ecosystem processes, biodiversity, and function. Because of this, there is concern about how climate change, intensification of groundwater withdrawals, and other human alterations may disrupt natural lake water level fluctuations and what such disruptions may mean for lake ecosystems. Unfortunately, while lake water quality has long been a core focus of lake management, there are comparatively few tools for describing or setting goals related to lake water quantity.
The Natural Flow Regime paradigm, which describes the importance of the magnitude, frequency, duration, rate of change, and timing of flow in streams, has been transformational for guiding water quantity management related to streams. However, hydrologic metrics used to describe stream flow regimes do not necessarily translate well to lake water level fluctuations due to differences in lake hydrologic behavior such as longer time scales of flood pulses. Here, we show how the Natural Flow Regime paradigm can be extended to lakes and we provide examples of lake-appropriate hydrologic metrics that are related to lake ecosystem function. We then use this framework to evaluate and compare the hydrologic regimes of over 40 lakes in Wisconsin, USA to illustrate a range of possible lake hydrologic regimes and discuss implications for lake water quantity management. For example, shallow seepage lakes located higher in the landscape tend to experience larger magnitudes of water level fluctuations than deeper drainage lakes located lower in the landscape and may be more sensitive to human or climate alterations that affect water quantity. We suggest that this framework for describing lake hydrologic regimes is a critical advance toward improved, comprehensive water quantity management.
