16 - Typology of water transport and chemical reactions in groundwater/lake ecotones

Summary

ABSTRACT Exchange reactions are important in the framework of subsurface flow between lakes and adjacent drainage basins. Frequently the groundwater/lake ecotones have the character of both a hydraulic barrier and a hydrochemical buffer. Consequently they exhibit a number of specific geohydraulic and hydrogeochemical features which are grouped into a coherent typology. It forms the basis of a multi-stage modelling approach, involving the professional groundwater model FLONET. The underlying measurements and deductions form part of the long-term German project ‘Ecosystem Research in the Bornhoved Lakes District’.

INTRODUCTION

Groundwater/lake ecotones as typically small interfaces control in a very specific way water and related chemical fluxes between lakes and their respective catchment. Therefore reliable material balances require a deeper understanding of the manifold hydrological phenomena related to the transport of solutes with its set of physical, chemical and microbial boundary conditions. Corresponding mathematical models reveal gaps in our knowledge (cf. Naiman & Decamps, 1990; Mitsch & Gosselink, 1992) which must be bridged in order to develop coherent and efficient strategies for the management of lakes in relation to the landuse patterns of their catchments. A necessary first step in this direction is the definition of a process-oriented typology of the water transport and chemical reaction phenomena in groundwater/lake ecotones.

In the present paper this definition is based on the longterm observations, measurements and modelling approaches of the German ‘Ecosystem Research in the Bornhoved Lakes District’ which is situated some 30 km south of Kiel and covering about 50 km² in terms of interrelated drainage basins (Blume et ai, 1992).