Terrestrial Water Storage Change Due to Human Activities

1. Terrestrial Water Storage Change Due to Human Activities Dork Sahagian Environmental Initiative Lehigh University

2. Who Cares about Sea Level Rise? Coastal Impacts

8. Sharp's Island, Maryland, ca. 1950. This photo shows what remained of an island that probably was approximately 700 acres in size at the time of original settlement in the late 17th century, and that still covered almost 600 acres in 1850. Until the first decades of the 20th century, Sharp's Island supported several large farms (at least one of 300 acres) and a hotel until 1910. Today, the island has disappeared, with only the historic Sharp's Island Light marking its former position.

10. NUMERICAL MODEL DEVELOPMENT Sparse and Infrequent Observations Management Directives Theoretical Misunderstanding Policy Oversimplified Formulation Code Errors Unrealistic Assumptions Confusion Further Misunderstanding Further Refinement of Unimportant Details Coincidental Agreement Between Theory and Observation Publication

11. #1 uncertainty! Causes of Sea Level Rise: 1. Glacial 2. OceanTemperature 3. Direct Anthropogenic changes in land storage

12. Synopsis • Account for past positive and negative anthropogenic contributions • Determine which will continue into the future • Normalize tide gauge and satellite records for above • Then use to assess glacial and thermal contributions • For future projections, include assessment of human activity

13. What to people do to cause sea level rise? • Ground Water Mining • Deforestation • Desertification • Wetland filling or drainage • Surface Water Diversion

14. GROUND WATER MINING Removal of fossil ground water from aquifers that do not appreciably recharge

16. Subsidence due to withdrawal from confined aquifer

17. SURFACE WATER DIVERSION

19. DESERTIFICATION

20. WETLAND DRAINING

21. TROPICAL DEFORESTATION

22. WATER STORED IN FORESTS Tropical Biomass = 45kg/m2 Dry/Fresh ratio = .25  3 parts water to 1 part biomass  135 kg/m2 vascular water = 13.5 cm water Biomass conversion O2+C6H10O5 5H2O+6CO2  1kg biomass + 0.55kg water so 45 kg/m2 biomass = 25 kg/m2 water = 2.5 cm water 2.5cm + 13.5cm = 16 cm water in plants Another 16 cm water in and around roots, soil moisture, leaves, etc. total32 cm water Tropical deforestation rate= 15.4x10(6) ha/yr = 15.4x10(10)m2/yr SO- 0.32m x 15.4x10(10)m2/yr = 4.93x10(10)m3/yr = 0.14mm/yr

23. ANTHROPOGENIC OCEANWARD WATER FLUX (SEA LEVEL RISE)

28. Global area covered by dammed reservoirs is 400,000 km2 75% of the world's dams and reservoirs have been built in the past 35 years, so the global rate of land loss from dam building is 0.75 x 400,000/ 35 = 8580 km2/ year

29. Why do we care about water impoundment?1. Impoundment increases local water resource stocks.2. Dams modify hydrographs- moderate flow variations.3. Dams trap sediment- fill reservoir, starve coast.4. Surface reservoirs evaporate- less total flow to coast.5. Reservoirs support different biota than rivers.6. Reservoirs add to oxygenation capacity - decompose wastes.7. New impoundment ameliorates sea level rise!

30. 1 cm •

32. WHAT IF WE STOP BUILDING NEW DAMS? SEA LEVEL WILL RISE FASTER!

33. Effect of dams on ground water Ground water filling = (KBt/n)1/2

34. Reservoir Capacity (km**3)

37. How to estimate volume impounded in small reservoirs? 1. Devise hydrologic land use classification scheme 2. Determine characteristic water impoundment 3. Measure areal extent of each class from remote sensing

39. Result- Total amount (rate) of impounded water Why? We need to know the rate at which we have been impounding water and creating new water resources for: 1. Water resource analysis 2. Sea level projections

40. BUT- Dams total does not include ground water or small dams!

41. DAMS 0.5 mm/yr from large reservoirs Add unknowns… 0.5 mm/yr from small, unregistered reservoirs 1 mm/y from impounded ground water

42. Sea level is rising! What to do? - Store more water on land?

43. Two issues: • Continue building dams at 20th century rate? (known social/environmental consequences) 2. Purposefully sequester additional water (Unforeseen consequences!)

44. Sequester more water on land? Some outrageous ideas: • Divert surface water • Pump water to high elevation dry basins • Build strategic dams • Enhance Antarctic precipitation

47. 1000 km Congo

48. Volume of “Congo Reservoir” Basin area below 500 m elevation = 1.1x1012 m2 Volume = 1.0 x 1014 m3 Ocean basin area = 3.6x1014 m2 SO- Flooding Congo lowers sea level by 28 cm! But don’t do it!

49. Summary • “Natural” and anthropogenic changes in various reservoirs • Uncertainties- small reservoirs, impounded ground water, aquifer mining rates, natural changes in ground water… • Critical gaps- dams inventory, ground water, climate effects • Recommendations- fill above gaps!

50. CONCLUSIONS Water storage on land changes due to natural and human factors Anthropogenic influences serve to both raise and lower sea level. (Most direct human activities raise sea level.) 2. Dams may completely counteract other human activities (and then some): • We have been “masking” the actual rate of 20th century sea level rise! • We must account for small impoundments. • We must account for ground water. 3. Several natural depressions could be filled with water: • How to get the water there? How to prevent it from leaving there? 4. There are some locations where large volumes can be stored behind dams. • Major new dams will cause major political and environmental disruption • Sea level amelioration would only be temporary 5. We need more complete inventories of land water storage reservoirs