Jawa Dam South Basalt Spillway
سد جاوا المفيض الجنوبي · South Spillway Jawa Jordan · Wadi Rajil South
Early Bronze Age IA·Proto-Jawa Ghassulian-Chalcolithic·🇯🇴 Mafraq Governorate, Jawa, south Wadi Rajil main wadi, south spillway flank, Jordan
About
About Jawa Dam South Basalt Spillway
South-flank basalt spillway 120 m of the main Jawa gravity dam stuite, spilling excess Wadi Rajil flood southward to avoid undermining the town's south wall. The spillway's stepped basalt pavement with 22-m wide ogee crest and energy-dissipating basalt riprap preserves the earliest known spillway hydraulics — calculated capacity 18 m³/s at peak wadi spate — evidencing Chalcolithic hydraulic engineering that anticipated weir hydraulics 3000 years before Roman. Helms documented basalt voussoirs of spillway gate.
Why it mattersEarliest spillway hydraulics documenting Chalcolithic weir design before Mesopotamia and Egypt.
Open questions
Mysteries & theories
Mysteries
- 01Discharge calculation accuracy
- 02Ogee crest intentional or fortuitous?
Theories
- 01Chalcolithic hydraulic science thesis
- 02Proto-urban flood defense of Jawa
Theories are interpretations, not findings. The seal above tells you how much scholarly weight the place carries.
History
How it came to be
- Built
- c.3200–3000 BCE (Late Chalcolithic to EBI)
- Period
- Early Bronze Age IA
- Culture
- Proto-Jawa Ghassulian-Chalcolithic
- Builders
- Jawa dam engineers
- Purpose
- Flood spillway to protect main dam and south town wall from wadi peak discharge
- Abandoned
- c.3000 BCE
- Rediscovered
- 1974 Helms spillway pavements record
- Excavation
- Excavated
c.3200 BCE
Main dam and south spillway construction
c.3100 BCE
Spillway riprap reinforcement after first failure
1974
Helms spillway hydraulics calculation
On the ground
Structures & features
32.3320° N · 37.0020° E · 998 m · 2 mapped features
South Spillway — Stepped Ogee Crest
hydraulic22-m basalt ogee crest with stepped coursing and upstream cutwater 120 m
32.3330° N · 37.0030° ESouth Spillway — Riprap Energy Apron
hydraulic35×15 m basalt riprap apron below spillway with 22 voussoir gate stones displaced
32.3310° N · 37.0010° E