Ecology of the alluvial aquifers of the Flathead River Montana

Stanford, Jack; Ward, J; Ellis, B

Stanford and Gaufin (1974) reported the presence of abundant insect larvae deep in the alluvia of the Tobacco River, a small gravel bed river in northwestern Montana. The insects were entrained in an infiltration gallery that provided potable water from the alluvial aquifer to the town of Eureka, Montana. The collection system was located ca. 150 m from the river and 3 m below the floodplain surface. The most abundant forms were stone flies (Plecoptera) of the genera Isocapnia and Paraperla. However, many other taxa, traditionally thought of as river macrobenthos, were also present, either actively or passively entering the collection system from the interstitial aquifer of the river. The discovery, coupled with the wide range in western North America of adult Isocapnia and Paraperla, led the authors to propose that the deep penetration of benthos into the saturated alluvia of gravel bedrivers was likely a widespread phenomenon that had significant ramifications for river ecology. A decade later Stanford and Ward (1988) confirmed the occurrence of the same Plecoptera, along with over 70 other invertebrate taxa, in the shallow alluvial aquifer of the much larger Flathead River in the Kalispell Valley; Plecoptera larvae were pumped from drilled wells on thevalley bottom up to 3 km from the river channel. Others working on interstitial fauna of gravel bed streams and rivers in Europe (Bretschko and Klemens, 1986; Danielopol, 1976), Canada (Colemanand Hynes, 1970; Pugsley and Hynes, 1986; Williams and Hynes, 1974),and elsewhere in the United States (Boulton et al., 1991, 1992; Palmer, 1990; Pennak and Ward, 1986; Ward and Voelz, 1990) also demonstrated speciose interstitial assemblages, but at the scale of meters or less. Based on the work summarized below and research on the Rhone River in France (Marmonier et al., 1992; Dole-Olivier et al.), it is clear that a diverse and abundant interstitial fauna may inhabit the alluvium of entire floodplains kilometers from the river channel. The long-term studies in the Flathead catchment now emphasize the four-dimensional nature of the riverine and floodplain landscapes (Ward, 1989) and the processes and implications related to water and materials exchange between floodplain alluvial aquifers and the river (Stanford and Ward, 1993). The purpose of this chapter is to summarize the data and interpretations linking the groundwaters and surface waters in the Flathead catchment. Much of the work remains unpublished, and some original data are included herein.

Ecology of the alluvial aquifers of the Flathead River Montana

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