| This paper describes the seasonal temperature development in the Akkajaure
reservoir, one of the largest Swedish reservoirs. It lies in the headwaters of the river
Lulealven in northern Sweden; it is 60 km long and 5 km wide with a maximum depth of 92 m.
The maximum allowed variation in surface water level is 30 m. The temperature field in
the reservoir is important for many biochemical processes. A one-dimensional lake model
of the Akkajaure reservoir is developed from a lake model by Sahlberg (1983 and 1988).
The dynamic eddy viscosity is calculated by a two equation turbulence model, a
k–ε model and the hypolimnic eddy diffusivity formulation which is a function
of the stability frequency (Hondzo et al., 1993). A comparison between calculated
and measured temperature profiles showed a maximum discrepancy of 0.5–1.0°C over
the period 1999-2002. Except for a few days in summer, the water temperature is vertically
homogeneous. Over that period of years, a weak stratification of temperature occurred on
only one to two weeks a year on different dates in July and August. This will have
biological consequences.
Keywords: temperature profile,reservoir, 1-D lake model, stratification, Sweden |