| Grand Coulee or Aswan | 21 |
| Go-with-the-flow thwarter | 25 |
| Glen Canyon structure | 21 |
| Gardiner or Mica | 16 |
| Flood controller | 16 |
| Flood control structure | 23 |
| Dental guard | 12 |
| Corps of Engineers project | 26 |
| China's Three Gorges, for one | 33 |
| China's Three Gorges ___ | 28 |
| Beavers' project | 20 |
| Beaver's structure | 22 |
| Beaver's construct | 22 |
| Beaver work | 11 |
| Beaver job | 10 |
| Beaver creek project | 20 |
| Beaver construction | 19 |
| Beaver barrier | 14 |
| Aswan, for one | 14 |
| Aswan project | 13 |
| Animal mother | 13 |
| What Sen. Norris gave | 21 |
| Waterwork? | 10 |
| Waterway barrier | 16 |
| Water checker? | 14 |
| Trotter's mom | 17 |
| Three Gorges, for one | 21 |
| Thing that can be very sticky? | 30 |
| The Gardiner, for one | 21 |
| System of a Down song that obstructs? | 37 |
| Structure with a spillway | 25 |
| Structure whose name might make kids giggle (3) | 47 |
| Stop from running | 17 |
| Somerset, in Vt. | 16 |
| Security gate? | 14 |
| River structure | 15 |
| River obstacle | 14 |
| Restrain a flow | 15 |
| Reservoir's edge | 20 |
| Reservoir creator | 17 |
| Rain check, at times | 20 |
| Provider of flower power? | 25 |
| Project of the Corps of Engineers | 33 |
| Power plant site | 16 |
| Pedigree listing | 16 |
| Oxbow, in Idaho | 15 |
| One that's holding back? | 28 |
| One going against the tide | 26 |
| Obstruction for salmon | 22 |
| Oahe, e.g. | 10 |
| Oahe is one | 11 |
| Nobelist in Medicine: 1943 | 26 |
| Mother among mammals | 20 |
| Mica or Gardiner | 16 |
| Maternal quadruped | 18 |
| Mare to foal | 12 |
| Levee's big brother | 23 |
| Leave it to beavers | 19 |
| Lake Mead sight | 15 |
| Keep from running | 17 |
| Johnstown's weak spot | 25 |
| ItÂ’s water resistant | 24 |
| It may get into deep water | 26 |
| It goes against the flow | 24 |
| It checks the water | 19 |
| Hydroelectric option | 20 |
| Hungry Horse or horse's mother | 34 |
| Hungry Horse is one | 19 |
| Horse's mother | 18 |
| Hoover, for instance. | 21 |
| Hoover, for example | 19 |
| Hoover or Roosevelt, e.g. | 25 |
| Hoover or Roosevelt | 19 |
| Hoover or Norris | 16 |
| Hoover or Cougar | 16 |
| Hoover or beaver | 16 |
| Hoover is one | 13 |
| Hoover -- | 9 |
| Hoover | 6 |
| Grand Coulee | 12 |
| Glen Canyon, e.g. | 17 |
| Gatehouse site | 14 |
| Gardner or Mica, for instance | 29 |
| Gardiner, for one | 17 |
| Four-legged mother | 18 |
| Fort Peck, for one | 18 |
| Fort Peck is one | 16 |
| Fort Peck ___, in Montana | 25 |
| Foal's mama | 15 |
| Flowage stopper | 15 |
| Flow checker | 12 |
| Flood-control project | 21 |
| Flood-control aid | 17 |
| Flood control project | 21 |
| Flood control | 13 |
| Flaming Gorge, e.g. | 19 |
| Fish ladder's spot | 22 |
| Fish ladder setting | 19 |
| Feature of Lake Mead | 20 |
| Create a reservoir | 18 |