Role of groundwater exchange on the energy budget and seasonal stratification of a shallow temperate lake

TY - JOUR

T1 - Role of groundwater exchange on the energy budget and seasonal stratification of a shallow temperate lake

AU - Kettle, A. J.

AU - Hughes, C.

AU - Unazi, G. A.

AU - Birch, L.

AU - Mohie-El-Din, H.

AU - Jones, M. R.

N1 - Funding Information: Laurie Cartwright, formerly of the University of East Anglia (UEA) field store, produced the UEA lake bathymetric information in 1981. Nick Ross and Ian Afford have kindly provided high resolution meteorological data in addition to making the information available for Internet download. We appreciate the assistance of the UEA teaching and research technical staff for facilitating this project. This work was supported by the following UK Natural Environmental Research Council (NERC) Grants: NER/I/S/2002/00678 to AJK, NER/G/S/2003/00024 to CH, NER/S/A/2006/14115 to MRJ . GAU was funded by the Ford Foundation. GAU, HMED, and LB were funded by the University of East Anglia (UEA) M.Sc. program.

PY - 2012/11/12

Y1 - 2012/11/12

N2 - An 18-month time series of the temperature and biogeochemical properties of a shallow, hyper-eutrophic lake was conducted in East Anglia, UK. The data show a seasonal stratification cycle that is typical of mid-latitude monomictic lakes with an overturning interval during the coldest part of winter. The existing paradigm suggests that this is due to the seasonal variation of the surface heat fluxes. However, sediment temperatures indicate that there may be significant bottom heating in winter and bottom cooling in summer. The temperature difference between the lowermost part of the lake water column and the underlying sediments shows a change of sign at approximately the start and end of summer stratification. An energy budget of the lake - calculated using vertical temperature profiles and atmospheric meteorological parameters - suggests that there may be a significant input of ground water below the thermocline of the lake. The groundwater heat flux term is calculated to be the second most important cooling factor after longwave radiation in the overall heat budget during the summer. The groundwater effect is more important than latent heat flux cooling for this lake, and this has important implications for the 'heat-budget method' that has been used to quantify evaporation from lakes. A time-resolved analysis suggests that there is little seasonal variation in the calculated groundwater flux and no clear correspondence with rainfall variations. Groundwater input to lakes may be more important than previously believed and may be an important factor of the overturning dynamics of some lakes.

AB - An 18-month time series of the temperature and biogeochemical properties of a shallow, hyper-eutrophic lake was conducted in East Anglia, UK. The data show a seasonal stratification cycle that is typical of mid-latitude monomictic lakes with an overturning interval during the coldest part of winter. The existing paradigm suggests that this is due to the seasonal variation of the surface heat fluxes. However, sediment temperatures indicate that there may be significant bottom heating in winter and bottom cooling in summer. The temperature difference between the lowermost part of the lake water column and the underlying sediments shows a change of sign at approximately the start and end of summer stratification. An energy budget of the lake - calculated using vertical temperature profiles and atmospheric meteorological parameters - suggests that there may be a significant input of ground water below the thermocline of the lake. The groundwater heat flux term is calculated to be the second most important cooling factor after longwave radiation in the overall heat budget during the summer. The groundwater effect is more important than latent heat flux cooling for this lake, and this has important implications for the 'heat-budget method' that has been used to quantify evaporation from lakes. A time-resolved analysis suggests that there is little seasonal variation in the calculated groundwater flux and no clear correspondence with rainfall variations. Groundwater input to lakes may be more important than previously believed and may be an important factor of the overturning dynamics of some lakes.

KW - East Anglia

KW - Eutrophic

KW - Groundwater

KW - Heat budget

KW - Lake

KW - Turbulent heat flux

UR - http://www.scopus.com/inward/record.url?scp=84868564613&partnerID=8YFLogxK

U2 - 10.1016/j.jhydrol.2012.07.004

DO - 10.1016/j.jhydrol.2012.07.004

M3 - Article

AN - SCOPUS:84868564613

VL - 470-471

SP - 12

EP - 27

JO - Journal of Hydrology

JF - Journal of Hydrology

ER -