Testing and evaluation of a HYMO classification system for lakes and reservoirs - Proposed new and modified hydromorphological (HYMO) classification system

Abstract

This project has tested and evaluated a hydromorphological (HYMO) classification system for lakes and reservoirs, published in 2018. The results revealed that applying the full set of parameters require extensive resources, and for some parameters data is hardly available. Based on the test results and the following evaluation, a revised version of a classification system is proposed. The revised system is divided into five classes, ranging from ‘near natural’ to ‘severely modified’ and consists of 17 HYMO parameters, in contrast to the original 30 parameters. The selected parameters are all considered being ecological relevant. The parameters are a mix of parameters describing alterations from natural conditions and degree of alterations. Many of the parameters can be calculated by employing hydrological models and with the use of digital bathymetric maps, if available. We have proposed a procedure for aggregating the individual parameter values into overall types of HYMO alterations, i.e. hydrological change, morphological change and barriers and fragmentation. Furthermore, we have proposed a system for screening of lakes and reservoirs with the purpose of sorting out those lakes that are either limited modified by HYMO alterations or extensively/ severely modified. This will reduce the number of lakes that will need to undergo a full classification