Государственное казенное учреждение Московской области
“Московская областная противопожарно-спасательная служба”
Ступинское территориальное управление силами и средствами 280 пожарная часть
Д. Петрово
In the very common case of rivers subject to seasonal flooding with much higher water levels for a relatively short period for example during monsoon season or snow melt and low and relatively constant water levels for the rest of the year it is best not to map the water extent during flooding. A useful rule of thumb would be to map the median of the maximum water levels of all months of the year. For those areas water covered during floods there are some ideas for tagging like Proposed features/floodplain and Key:flood_prone.
Rivers with a fairly constant water level for most of the year often have a clearly visible (though sometimes frequently changing) river bed indicating the normal extent of the river even during the dry season when the actual water levels are much lower.
In case of intermittent rivers it makes sense to map the water extent at times the river is not dry and add intermittent=yes. Care should be taken in regions were water is diverted from the river for irrigation and other purposes since the river often does no more fill the river bed even during the wet season in such cases.
literan
Внесу ясность - когда я писал про “большую воду” (в теме откатов) речь шла о водохранилищах и озёрах, изначальный вопрос Alex Nemo ровно про это. Про реки понятно что другая история.