Predicting the date of lake ice breakup

Standard deviations for lake breakup dates were calculated for all lakes in Canada with reasonably long breakup records and for five lakes in Wisconsin with long-term records. Standard deviations were about 13 days for coastal lakes and 7-11 days for continental lakes. The accuracy of the melting degree day method of predicting breakup dates were investigated for 12 of these lakes; standard deviations ranged from 3.3-8.0 days. Regression equations for predicting breakup dates were developed from past breakup and air temperature records for the 12 lakes; standard errors ranged from 1.6-4.3 days. General forecast guidelines were developed for application to lakes with limited breakup records. The equations and forecast guidelines are suitable only for continental lakes where wind and river inflow effects are not dominant.Les d\ue9viations normales des dates de d\ue9gel sont calcul\ue9es pour tous les lacs du Canada o\uf9 des dossiers assez complets ont \ue9t\ue9 tenus et pour cinq lacs du Wisconsin couverts par de longs dossiers. La pr\ue9cision avec laquelle il est possible de pr\ue9dire le d\ue9gel a \ue9t\ue9 \ue9valu\ue9e pour douze de ces lacs en utilisant les dossiers de d\ue9gel et de temp\ue9rature de l'air. Deux moyens de pr\ue9diction ont \ue9t\ue9 employ\ue9s: la m\ue9thode des degr\ue9s-jours de fonte et la m\ue9thode de l'\ue9quation de r\ue9gression. Des \ue9quations g\ue9n\ue9rales sont \ue9tablies afin de permettre des pr\ue9dictions pour les lacs o\uf9 les dossiers sont incomplets.Peer reviewed: NoNRC publication: Ye