Presentation on theme: "Terrestrial Water Storage Change Due to Human Activities Dork Sahagian Environmental Initiative Lehigh University."— Presentation transcript:
Terrestrial Water Storage Change Due to Human Activities Dork Sahagian Environmental Initiative Lehigh University
Who Cares about Sea Level Rise? Coastal Impacts
Sharp's Island, Maryland, ca 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 17 th century, and that still covered almost 600 acres in Until the first decades of the 20 th century, Sharp's Island supported several large farms (at least one of 300 acres) and a hotel until Today, the island has disappeared, with only the historic Sharp's Island Light marking its former position.
NUMERICAL MODEL DEVELOPMENT Sparse and Infrequent Observations Theoretical Misunderstanding Oversimplified Formulation Code Errors Unrealistic Assumptions Confusion Further Misunderstanding Further Refinement of Unimportant Details Coincidental Agreement Between Theory and Observation Publication Policy Management Directives
Causes of Sea Level Rise: #1 uncertainty! 1. Glacial 2. Ocean Temperature 3. Direct Anthropogenic changes in land storage
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
What to people do to cause sea level rise? Ground Water Mining Deforestation Desertification Wetland filling or drainage Surface Water Diversion
GROUND WATER MINING Removal of fossil ground water from aquifers that do not appreciably recharge
Subsidence due to withdrawal from confined aquifer
SURFACE WATER DIVERSION
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 kg water so 45 kg/m2 biomass = 25 kg/m2 water = 2.5 cm water 2.5cm cm = 16 cm water in plants Another 16 cm water in and around roots, soil moisture, leaves, etc. total 32 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
ANTHROPOGENIC OCEANWARD WATER FLUX (SEA LEVEL RISE)
Global area covered by dammed reservoirs is 400,000 km 2 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 km 2 / year
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!
WHAT IF WE STOP BUILDING NEW DAMS? SEA LEVEL WILL RISE FASTER!
Effect of dams on ground water Ground water filling = (KBt/n) 1/2
Reservoir Capacity (km**3)
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
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
BUT- Dams total does not include ground water or small 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
Sea level is rising! What to do? - Store more water on land?
Two issues: 1. Continue building dams at 20th century rate? (known social/environmental consequences) 2. Purposefully sequester additional water (Unforeseen consequences!)
Sequester more water on land? Some outrageous ideas: Divert surface water Pump water to high elevation dry basins Build strategic dams Enhance Antarctic precipitation
1000 km Congo
Volume of “Congo Reservoir” Basin area below 500 m elevation = 1.1x10 12 m 2 Volume = 1.0 x m 3 Ocean basin area = 3.6x10 14 m 2 SO- Flooding Congo lowers sea level by 28 cm! But don’t do it!
“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!
CONCLUSIONS 1. Water storage on land changes due to natural and human factors 2. 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
Suggestions: (a humble opinion) 1. Address causes of sea level rise: ACTUAL mitigation (by new technologies, macroengineering or otherwise) of warming due to greenhouse gas emissions, land use 2. Better predict 21st century sea level rise (with, without mitigation) 3. Adapt strategically to predicted unavoidable sea level rise 4. Do not give the impression that actual climate change mitigation is unnecessary or impossible BOTTOM LINE- Need a “diversified portfolio” of approaches to mitigation, sequestration and adaptation.
Example of Hydrological Land Use Classification Scheme 1. Moist temperate/boreal agricultural (>100cm/yr precipitation) 2. Moist tropical/subtropical agricultural (>100cm/yr) 3. Intermediate temperate agricultural ( cm/yr) 4. Intermediate tropical/subtropical agricultural (40-100cm/yr) 5. Semi-arid agricultural (<40cm/yr) 6. Pasture/rangeland 7. Urban and other densely populated non-agricultural regions (>100cm/yr) 8. Urban and other densely populated non-agricultural regions (<100m/yr)
Direct extrapolation branch Unmixing branch Logical flowchart 1. Construct a global map of bio-hydro- climatological zones (direct branch) 2. Construct a map of irrigated/non-irrigated agriculture based on time series analysis of precipitation and moisture index, calibrated using field and Landsat data (direct branch) 3. Calculate small impoundment water volume per unit area using Landsat and field studies (direct branch) 4. Estimate small impoundment areas by unmixing MODIS, based on Landsat training data (unmixing branch) 5. Calculate total impounded water volume by multiplying the water volume per area in a zone by the total area of the zone (direct branch) and by transforming the unmixed area maps (unmixing branch) to volumes using field data
Land surface models provide insights, but more data are needed. Spatial resolution insufficient to address specific anthropogenic influences
Direct extrapolation branch Unmixing branch Logical flowchart 1. Construct a global map of bio-hydro- climatologic zones (direct branch) 2. Construct a map of irrigated/non-irrigated agriculture based on time series analysis of precipitation and moisture index, calibrated using field and Landsat data (direct branch) 3. Calculate small impoundment water volume per unit area using Landsat and field studies (direct branch) 4. Estimate small impoundment areas by unmixing MODIS, based on Landsat training data (unmixing branch) 5. Calculate total impounded water volume by multiplying the water volume per area in a zone by the total area of the zone (direct branch) and by transforming the unmixed area maps (unmixing branch) to volumes using field data