3.7　Ice Regime Survey

3.7.1　For the ice regime survey，the measured ice regime data from ocean，river and lake observation stations，as well as the ice regime investigation and census data from oceanic and water sources（water）authorities shall be collected.

3.7.2　The characteristic values of ice regime necessary for nuclear power engineering shall be surveyed based on water bodies such as rivers，lakes（reservoirs），and seashore（estuaries）.

1　The survey on ice regime of rivers shall cover the earliest and latest occurrence date of frazil ice，drift ice，freezing over，break-up and end ice；typical and maximum duration（days）of drift period and freezing period；typical and maximum size of drift ice during the drift period near the site，velocity，and the maximum water level of drift ice；the maximum thickness and width of shore ice during freezing period，the thickness and occurrence of ice flower，effective water depth，the start and end time of freezing-through，water flow on the ice，snow on the ice and ice formation within water；the method and probability of ice break-up；the occurrence date，location，scale and severity of ice jam and ice dam in the design river reaches，the highest backwater level and affected distance；the operation mode of upstream and downstream hydropower stations or reservoirs during ice period and the influence on ice regime of the design reaches.

2　The survey on ice regime of lakes（reservoirs）shall cover the earliest and latest occurrence date of frazil ice，drift ice，shore ice and end ice；the duration（days）of drift ice and shore ice；sizes and direction of drift ice or floating ice and their effects on the hydraulic buildings（structures）；the maximum water level of drift ice，the drifting and condensation of floating ice flowers and ice flowers；the maximum and typical thickness of shore ice of lakes（reservoirs）and the maximum accumulative height；the scale，influenced range and maximum jam level of ice dam and ice jam at the estuaries of rivers and end of the backwater area in reservoirs.

3　The survey on ice regime of seashores（estuaries）shall cover the earliest and latest occurrence date of frazil ice，drift ice，shore ice，fast ice and end ice；the duration of drift ice，shore ice and fast ice；the maximum and typical size of drift ice blocks nearby the project location and their velocity and drifting direction；the thickness，width and accumulative height of shore ice.For tidal reaches，the movement of ice layers in two directions shall be investigated.

3.7.3　For water areas which may expose the site and its vicinity to ice jam，embacle and ice dam shall be a focus in survey.

3.7.4　Where data on the ice regime of the site is unavailable，the data of adjacent hydrologic stations with severer ice regime can be used.Alternatively，estimation can be made by referencing the change of ice regime before and after the construction of adjacent works in conjunction with site investigation，or the ice regime characteristics of the design area can be determined by observing the ice regime through a winter and a spring and comparing the observed data with long-term observation of an adjacent station.