This Technical Report (TR) provides guidance to assist with the planning and design of Hydrometric networks, to ensure a better understanding of the water cycle, and that any data are observed and collated in an effective and appropriate manner. The TR is intended for use when:- • a new network is being planned and designed; • the nature, value and extent of an existing network is being reviewed; • a redundant network is being decommissioned or modified. This is to ensure that the impacts of these changes are considered objectively, and all changes are adequately monitored and recorded. This TR covers all aspects that are considered pertinent to the evaluation. The information will be used to inform the decision-making process employed by the network’s owners and operators. The objective nature of the review will ensure that all influential factors, both beneficial and otherwise, are considered. This will ensure that primary and potential alternative uses of the network are considered. It will also ensure compliance with any extant environmental legislation.