Prediction of lake levels using water balance models

Simple water balance models can be used to predict excess water and when 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 quarters have shown significant reductions and subsequent increases during 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 determined using a WATBAL type model for the current land-use distribution. The depth of the lake has been modelled using rainfall and excess water as inputs and evaporation as output. Given the simplicity of the model the agreement between measured and predicted lake levels is very good. (C) 1997 CSIRO Published by Elsevier Science Ltd.