the.com/weir
a fence built of water, quietly bossing rivers around since the Romans
means A low dam or barrier built across a river to control its flow or raise the water level, often letting water spill over the top.
from From Old English 'wer,' meaning a dam or fence for catching fish, related to the verb 'werian,' to defend or guard — so a weir was originally something that fenced in or held back, a cousin to the idea of 'wear' in the sense of warding off. The fishing sense came first: barriers that trapped fish were ancient long before weirs were repurposed to manage water levels for mills and navigation.
- job
- raises upstream water to control downstream flow
- silent killer
- recirculating currents trap and drown swimmers
- old tech
- used for fishing and milling since antiquity
- the V trick
- V-shaped weirs measure exact water discharge rates
- eel highway
- some include passes so fish climb past them
aswan high dam — egypt's massive weir on the nile river, completed 1970, creates lake nasser
trinity weir — dublin's weir on the river liffey, built 1816, controls tidal flow in city center
carew castle weir — medieval tidal weir in pembrokeshire, wales, still visible at carew river