Epsilon Archive for Student Projects

Abstract

The water level of Lake Mälaren has been regulated since the 1940’s. A recent
investigation suggests that the current regulation needs to be adjusted in order to
prevent a decline in water level, salt water from infiltrating from Lake Saltsjön,
and risk of floodings. In addition to these preventions, the new regulation could
potentially effect the natural environment and agriculture practices in the low
lands that surround the lake. The new regulation proposal calls for an increase in
variations in Mälaren’s water level during seasons, while the annual mean water
level will remain the same. The Swedish Agriculture Industry has been given a lot
of restrictions by the Swedish government in order to decrease it’s nitrogen leakage
to ground and surface water. Nitrogen is very much affected by the water content
in the soil through microbial activity as well as for transportation in the soil.
The aim of this thesis was to investigate how the water flow in the soil in lowland
areas around lake Mälaren would change with the proposed regulation. Based on
results from the modelling program Drainmod. A comparison was made between
the old regulation and the new regulation proposal. Based on the Drainmod results,
the differences in nitrate-nitrogen flow to ground water and fictitious spring crop
production are likely to be minimal between the two regulation proposals. In the
new regulation there is a possibility for delayed spring agricultural tilling due to a
higher water level during the spring season. Over the whole period of 30 years, the
old regulation has a slightly bigger runoff volume which indicates a possible
greater loss of nitrogen. There are differences between the input data and the actual
simulated data for the precipitation in the model which gives reason to question
the results in this study.