Story line for the B2C ground water exhibit

Our exhibit has three modules focussed on (1) the hydrologic cycle, (2) contaminant transport, and (3) water issues in the Tucson Basin. We like to get across the following concepts:

• water cycle
• ground water flow, recharge/discharge, ground water/surface water interactions, flow through sediments and fractured rocks
• ground water contaminant transport
• water quanity and quality issues in the Tucson Basin

• in undergraduate and graduate courses at B2C,
• in B2C highschool summer programs,
• as part of the regular B2C tourist tour, several scheduled 'performances' per day.

View of the exhibit from the top:

• Lights are suspended from the ceiling to illuminate the exhibit, in particular the two sand boxes.
• A timer periodically produces rain and injects dye into the landfill area in the 3D and 2D models
• The relative arrangement of the three elements is subject to the geometry of the exhibit space. The big sand box needs to be viewed from the lower right corner.
• View of the sandbox and cabinet with installed pumps during construction phase low res image

Module 1: The water cycle (right)

Key points:

• water cycle, global water budget
• ground water flows from high to low elevation
• ground water/surface water interaction
• recharge/discharge

Header: 1. The water cycle

Text:

In the Tucson area, most precipitation falls in the mountains as rain and snow, about 1000 mm (40 inches)/year on Mt. Lemmon versus 300 mm (12 inches)/year  in downtown Tucson. Most of this water either evaporates immediately or runs off on the surface into rivers and lakes. Water enters the ground (infiltrates) mostly through fractures in the mountains and through coarse sediments underneath the stream beds. Ground water, like surface water, flows basically from high to low elevation. However, because ground water flows a lot slower than surface water, ground water in the Tucson Basin can be up to several thousand years old, and may have formed under different climate conditions.

Figures:

• Fig 1.1 Global water cycle
• (low res image, jpg)(high res images, AI)
• Source: M. Stute, Lamont-Doherty Earth Observatory, 2002
• Caption: Water evaporating over the oceans is transported by wind, condenses to form clouds, and falls to Earth as rain or snow. Most of it immediately returns to the atmosphere by evaporation or transpiration (loss of water from plants). Part of it runs off on the surface and forms lakes and rivers. The remainder soaks into the ground, some of which recharges aquifers (permeable geological formations that produce water) and becomes ground water.  Surface water and ground water eventually flow into the ocean or evaporate/transpire back into the atmosphere to complete the water cycle.

• Fig 1.2 Global water budget
• (low res image)(MS Excel file)
• Source: after Berner and Berner, 1987
• Caption: Only very little of the Earth's water is available for our use. More than 97% of the water on our planet is in the oceans and is  too salty for consumption. Less than 1% of all water on Earth is available to support life on land.

• Fig 1.3 Gaining and losing streams
• (low res image)(high res image, Illustrator)
• Source: after Winter et al., USGS Circular 1139, 1998

Caption: Surface and ground water are often connected, and water can flow in either direction depending on the elevation of the stream or lake relative to the water table in the aquifer. Lowering of the water table  by over-pumping or drought may result in stream beds drying up, causing the subsequent death of vegetation and animals. Artificial recharge through stream channels can raise ground water levels. The water table is the level to which water rises in a shallow well in the uppermost aquifer.

Module 2: Ground water contamination (middle)

Key points:

• typical sources of contaminants
• typical contaminants
• migration of contaminants in the subsurface can be very complicated
• pumping might influence the movement
• despite the fact that clean-up technologies are available, prevention is the most important strategy

Header: 2. Ground water contamination

Text:

Figures:

• Fig 2.1 Typical sources of ground water contaminants
• (low res image)(Adobe Illustrator file)
• Source: after Hemond & Fechner-Levy, 2000
• Caption: Groundwater is vulnerable to contamination from leaking landfills and fuel tanks, discharge from industrial plants, septic tanks, and from agricultural activities, just to name a few. Some of these contaminants dissolve in water. Others do not dissolve well and float on top of the aquifer or sink to the bottom. The migration of contaminants is influenced by their chemical properties, the geology of the aquifer and also by how much water is pumped out of the aquifer.
• Fig 2.2 Contaminant plumes at the Broadway/Pantano landfill site
• (low res image) (Abobe Illustrator file)
• Source: Arizona Department of Environmental Quality, 2002

Caption: This municipal landfill is located in east-central Tucson and was operated until 1971. In 1987, tetrachloroethene (PCE) was detected in a city well located at the western edge of the landfill.  Since then trichloroethene (TCE), and vinyl chloride have also been found in ground water at levels exceeding regulatory standards. The city of Tucson Water Department (Tucson Water) has lost the use of four municipal wells in its Central Wellfield as a result of the contamination. The contaminants have reached the water table by vapor transport through the unsaturated soil.  A soil vapor and ground water containment system will be operational at the landfill in 2002. The map shows the extent of the PCE contamination plumes where the concentrations exceed the regulatory standards (5 micrograms/liter (µg/l)).

Module 3: Tucson basin (left)

Key points:

• unbalanced water budget
• consequences of water mining, in particular subsidence
• past, present & future
• drying of rivers as consequence of drop in water table

Header: Water in the Tucson Basin

Text:

Figures:

• Fig 3.1 Aerial view of the northern section of the Tucson Basin reflected in the sand tank model
• pictures would be placed above the sandtank model to show what the model corresponds to in the real world.
• low res image, (high res image, TIF)
• please make sure that the copyright as shown on the low res image goes on the high res as well.
• Source: P. Kresan, University of Arizona, 2002
• Caption: Aerial view of the northern section of the Tucson Basin reflected in the sand tank model.
• Fig 3.2 The Tucson Basin from above and location of the sand tank model
• low res image, high res image
• Source: R. Butler and M. Wallace, The Saguaro Project, University of Arizona, 2002
• Caption: The Tucson Basin from above, and location of the sand tank model (red box), and the geological cross section in Fig 3.3 (blue line).
• Fig 3.3 Schematic vertical cross section through the Tucson Basin
• low res image (high res simage, Illustrator file)
• Source: B. Scarborough, Desert Museum, 2002
• Caption: The Tucson Basin is like a large bathtub filled with sediments surrounded by mountains. The basin aquifers are recharged mostly by water coming from the mountains, where it rains more than in the valley. In general, water quality decreases in the older and deeper sediments.
• Fig 3.4 Approximate decline in ground water levels , 1940-1995
• low res image, high res image
• Source: Water Resources Research Center, University of Arizona, 1999; Tucson Water, 2002
• figure would be combined with one hydrograph as an example (well C-033A), in center of depression cone (see black star in -200ft zone  in low re image)  low res image (Excel data file)
• Caption: The water table in Tucson has steadily declined over the last 50 years as shown here for one Tucson Water well. In  some places the water table has fallen by more than 60 m (200 feet). As the aquifer loses water, it becomes compacted and the land surface subsides.Stream beds run dry and cannot support plant and animal life.

Additional potential figures

• Fig 3.x Water Demand and Supply in the Tucson AMA (1997 conditions) Should contact ADWR for updated information.
• low res image
• Source: Gelt et al., 1999
• Caption:
• Fig 3.x The growth of the City of Tucson
• low res image
• Source: Gelt et al., 1999
• Caption:
• Fig. 3.x Ground water table and flow direction in Tucson
• low res image, high res. image
• Source: Gelt et al., 1999; ADWR
• Caption:
• Fig 3.x Movement of recharged water through the aquifer
• low res image
• Source: Gelt et al., 1999
• Caption:
• Fig 3.x View of the sandbox and cabinet with installed pumps
• low res image
• Source: M. Stute
• Caption:

• precipitation distribution
• ground water flow pattern
• cube with cross section of the box, 3D
• illustrated with historical photographs
• growth of Tucson (fig 2-4, WRRC99)
• lowered water tables for cube area
• map of lowered water table in whole area
• future scenarios, budgets incl. CAP water

For more information visit http://www.bio2.columbia.edu/water/

• website will provide the following
• motivation why this exhibit is at the Biosphere
• details of the construction
• links to key publications
• links to major sites focussed on the Tucson Water sistuation
• links to sponsors (EMSI, SAHRA, Tucson Water, etc.)

Acknowledgements

We also like to thank the following individuals for their support of this project:

• M. Basefsky, Tucson Water
• A. Borden, undergraduate student, B2C
• R. Butler, University of Arizona
• P. Catanzaro, Columbia University
• L. Ehman, Arizona Department of Environmental Quality
• B. Ekwurzel, University of Arizona
• G. Flynn, Columbia Universiy
• L. Key, Environmental Education Exchange
• R. Marra, Tucson Water
• B. Prior, Tucson Water
• D. Rucker, University of Arizona
• B. Scarborough, Desert Museum
• E. Spangenberg, University of Wisconsin
• S. Pfirman, Barnard College
• C. Stute
• M. Stute, Barnard College and B2C
• B. Tellman, Water Resources Research Center, UofA
• G. Wagenseller, Arizona Department of Environmental Quality
• M. Wallace, University of Arizona
• J. Washburne, UofA
• and many others.