An Overview of Springs Ecosystem Ecohydrogeology and Conservation.

Authors: Lawrence Stevens, Joseph Holway

Year: 2025

Abstract

In this presentation we provide an overview of contemporary understanding of the ecohydrogeology of springs. Spring ecosystems develop where groundwater reaches the planetary surface, on land and under water. Springs are patchily distributed but abundant, perhaps with 20 million on Earth, and are distinctively individualistic ecosystems that provide the baseflow of most rivers in non-glaciated landscapes. Despite their generally small size, springs often support elevated within-site biodiversity of listed, endemic, rare, and poorly known taxa, as well as many undescribed lineages, adding substantially to regional gamma-diversity. Although springs account for less than 0.001% of terrestrial landscapes in the USA they support approximately 15% of the nation’s endangered species. Preliminarily, we documented more than 330 species of springs-dependent aquatic and riparian macro-taxa in the Colorado River basin in the seven southwestern basin states. Springs function as keystone ecosystems – often isolated habitat patches that are highly ecologically interactive as keystone ecosystems, supporting complex intrinsic assemblages as well as a great many upland species. In addition to their ecological significance, springs are cultural hotspots, holding deep significance for indigenous and dominant societies, and globally providing hundreds of billions of dollars in essential goods and services to billions of people worldwide. Despite their obvious significance and the well-studied field of groundwater hydrogeology, the characteristics, processes, and roles of spring ecosystems remain egregiously neglected and lack adequate stewardship and protection policies. Springs are threatened everywhere by groundwater withdrawal, under-informed land use practices, and climate change and, as throughout the world, the biota and conservation status of most North American springs remains largely unknown. Analysis of several thousand springs in the Basin and Range province of Nevada (USA’s driest state) revealed that >85% of springs there are impaired, more than two thirds of them seriously so. Declines in springs discharge align with recent findings on the dramatic depletion of groundwater levels across the nation over the past century. Although monitoring data are rare, analyses of long-term USGS streamflow data shows that 56% of gauged springs across the country, and nearly all large springs in the southwestern USA, have significantly declined in discharge over the past several decades. For example, central Arizona’s Del Rio Springs are the headwaters of the Wild and Scenic Verde River, but mean annual discharge decreased from 57 to <1 L/sec from 1996-2024 due to unregulated groundwater pumping of the Big Chino Aquifer and failing infiltration due to climate change. Declines in springs discharge have direct impacts on stream discharge and the diverse biota supported in these groundwater-fed habitats. From 2008-2022 Verde River baseflow decreased by 16% compared to 1993-2007. Only three of the 13 native fish species populations (including two listed species) remain in the middle reaches of that river. Now, as throughout our evolutionary history, springs serve as critical habitat for humanity, and their socio-ecological importance is increasing as current population and climate trends continue, not only in arid and semi-arid regions, but globally. On-going groundwater exploitation and climate warming are reducing infiltration and, consequently springs discharge and populations of the biota they support. The springs biome is everywhere undergoing a profound but largely ignored biodiversity crisis, one that warrants significant scientific, public, and governmental attention and action. Although the loss of springs is a dire issue, multiple restoration projects have demonstrated that, if the supporting aquifer is relatively intact, spring ecosystems can be relatively easily rehabilitated and managed to better balance ecological and economic values.