Knowledge of catchment hydrology is essential for interpreting weathering reactions. It is not only weathering reaction which contribute to the observed chemical composition of a river; rain, snow and melting ice also contribute. The contribution of the precipitation inputs can be estimated with careful monitoring and the use of chemical analyses. For some elements, like Cl, precipitation is the main source. It is possible roughly correct stream water data for precipitation inputs using such elements.
Both catchments will have different temporal patterns of discharge.
Fardalen: Discharge is expected to be controlled by snow-melt at the start of the season. Once the snow has melted, rain events will likely lead to temporary increases in discharge.
Dryadbreen: Discharge is also expected to be controlled by snow-melt at the start of the season, thereafter ice-melt from the glacier will contribute to discharge.
Ice covered areas can be divided into valley glaciers such as those found in the European Alps and ice caps like those which cover Greenland and Antarctica.
Valley glaciers can be further divided into three groups depending on how warm the bottom of the glacier is - even if the air temperatures are well below freezing, the weight of ice in thick glaciers results in pressure melting and means that temperatures at the base of glaciers can be above freezing. The three types are:
Dryadbreen is likely to be cold-based because it isn't so thick and is relatively small. This means that most of the meltwater flows over the glacier in supra-glacial channels and down the sides of the glacier. To confirm which type of glacier Dryadreen is, we need to closely monitor the discharge and chemical composition of the meltwater over a melt season.