Simple water balance models can be used to predict excess water and wh
en the depth-volume relationship for a lake is known, these models can
be used to predict variations in lake level. In the lake Goran study
area annual rainfalls have varied significantly. The straight line of
best fit shows a very slow increase over 116 years. An examination of
the seasonal distribution of the rainfall reveals significant changes
over that period. The October to December and the January to March qua
rters have shown significant reductions and subsequent increases durin
g the recording period. In the early 1990s the April to June rainfalls
have shown a significant increase and, coupled with comparatively low
evaporation and transpiration at that time of the year, this has lead
to significant increases in runoff. The excess water has been determi
ned using a WATBAL type model for the current land-use distribution. T
he depth of the lake has been modelled using rainfall and excess water
as inputs and evaporation as output. Given the simplicity of the mode
l the agreement between measured and predicted lake levels is very goo
d. (C) 1997 CSIRO Published by Elsevier Science Ltd.