Water saving basins Lock (water navigation)

disused side pond @ atherstone on coventry canal, england

a way of reducing water used lock give 1 or multiple reservoirs, levels intermediate between upper , lower pounds. these reservoirs can store water drained lock boat descends, , release fill next time boat ascends. saves half amount of water lost downhill in each fill-empty cycle. these reservoirs called saving basins .

installing single side pond save 1/3 of water, whereas 3 side ponds save 60% of water: first 1/5 of water goes top pond, 2nd 1/5 middle pond, 3rd 1/5 bottom pond – , 2/5 wasted @ each passage (assuming area of each pond equals area of lock). formula



n


{\displaystyle n}

side ponds of optimal altitude , depth, area of each pond,




a

p




{\displaystyle a_{p}}

, , area of lock,




a

l




{\displaystyle a_{l}}

, is:

water used side ponds
water used without side ponds


=
1
−


n

n
+
1
+

a

l



/


a

p







{\displaystyle {\frac {\text{water used side ponds}}{\text{water used without side ponds}}}=1-{\frac {n}{n+1+a_{l}/a_{p}}}}

.

diagram of water saving basins (descending)



diagram of water saving basins (ascending)

for example, hindenburg-lock (in hannover, germany, built 1919–1928) has 2 lock chambers of 225 m length, each of use 42,000 m³ of water full locking cycle. due use of 10 water saving basins, 10,500 m³ of water used. more recent example rhine–main–danube canal 13 saving locks out of total of 16 locks.

water saving basins incorporated in proposals augment capacity of panama canal, scheme controversial because mixing of salt , fresh water in basins allow brackish water gatun lake, source of drinking water , wildlife reserve.

map showing extended intermediate pounds @ caen hill locks

on english canals, these reservoirs called side ponds . droitwich canal, reopened in 2011, has flight of 3 locks @ hanbury have operational side ponds. side ponds installed on grand union canal , coventry canal, among others. out of use, , in cases have been filled in, because british waterways considered easy misuse them , flood surrounding area. on flights of locks short intermediate pounds, pounds extended sideways – in effect provide reservoir ensure pound not run dry (in case, instance, lock below leaks more lock above). these extended intermediate pounds confused side ponds.