The significance of groundwater-surface water interactions on hyporheic physico-chemistry and stream ecology in two Scottish mountain rivers

• Main Author: Grant, Jane D.
• Published: University of Aberdeen 2008
• Subjects: 591.7; Groundwater : Groundwater ecology : Atlantic salmon
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499118

This research investigated the ecological significance of GW-SW interactions in the hyporheic zone of two Scottish mountain rivers (the Girnock Burn and the River Feshie).  The research comprised three components: (i) an assessment of the influence of GW-SW interactions on the spatio-temporal variability of hyporheic hydrochemistry and macroinvertebrate community structure, (ii) an evaluation of the influence of GW-SW dynamics on small-scale spatio-temporal variability in hyporheic thermal regimes, and (iii) an investigation of the spatial relationship between Atlantic salmon <i>Salmo salar </i>(L.) spawning distributions and patterns of GW-SW exchange in a braided river reach. In the Girnock, marked inter- and intra-reach differences in hyporheic water quality were found and linked to spatio-temporal variability in GW-SW exchange.  Up to 25% of the spatial variability in invertebrate community structure could be accounted for by differences in hyporheic water quality.  Community composition varied markedly between winter, spring and summer seasons, with the relative importance of individual water quality variables differing between seasons. There was much heterogeneity in streambed temperature regimes across the study reaches, with data suggesting that long-residence groundwater contributed significantly to hyporheic exchange.  However, at small (cm to m) scales thermal variability was most likely explained by the interaction of reach-scale GW-SW exchanges with smaller-scale, current-bed form induced hyporheic exchange. In a braided section of the River Feshie, spatially complex and temporally dynamic GW-SW exchange patterns occurred.  Salmon spawning was concentrated in locations characterised by upwelling groundwater at depth, with up to 66% of spawning sites recorded in groundwater dominated channels.