HYDROLOGY IN A CHANGING CLIMATE: MOUNTAINS AS WATER TOWERS

1. HYDROLOGY IN A CHANGING CLIMATE: MOUNTAINS AS WATER TOWERS Mark Williams University of Colorado Geography and INSTAAR

2. What Do We Really Know about the Water Cycle? • Water flows towards money • Whiskey’s for drinkin’, water’s for fighten’

3. WATER CYCLE

4. HYDROLOGIC EQUATION Q = P – ET +- DS Q is discharge P is precipitation ET is evapotranspiration S is storage (usually groundwater)

6. GLOBAL WATER USERS

7. INCREASING GLOBAL USE OF WATER

8. We aren’t making new water!

9. WATER RESTRICTIONS • Apply only to municipal water users • They use <10% of all water • Why are municipal water users picked on? • Should municipal water users adhere to voluntary water restrictions? • Or by doing so do they provide aid and comfort to water abusers?

10. MOUNTAINS AS WATER TOWERS

12. AREAS DEPENDENT ON MOUNTAIN DISCHARGE DANIEL VIVIROLI, ROLFWEINGARTNER and BRUNO MESSERLI

13. GLOBAL VIEW OF MOUNTAIN DISCHARGE DANIEL VIVIROLI, ROLF WEINGARTNER and BRUNO MESSERLI

14. Headwaters of almost all Major Rivers in Mountains

15. Transfers water 13 miles from Lake Granby, Shadow Mountain Lake and Grand Lake (in the Colorado River basin) to the Big Thompson River for use on the east slope of the Front Range, under Rocky Mtn NP via Adams tunnel Most water users prefer “mountain stream water” because gravity delivers it for free. Gravity is Free: The Colorado-Big Thompson diversion project

16. Potable Drinking Water • Dependable, potable water as a renewable resource is one of the global environmental obstacles that has grown more acute as a result of population increase and changes in global climate patterns.

17. WATER QUALITY New York City Storage capacity of 550 billion gallons. 1.5 billion gallons per day delivered to 9 million customers 97 percent reaches homes and businesses through gravity alone 90% of water unfiltered. Chlorine is added to the water to kill bacteria, and fluoride is added to help prevent tooth decay. ALL WATER FROM MOUNTAINS!

18. Brewed with Pure Rocky Mountain Spring Runoff

19. Benefits of Mountain Runoff • Mountain runoff provides 65-90% of usable water in arid and semi-arid regions • The high quality of mountain runoff is preferred for drinking water, beer making • Mountain runoff is “free” to downstream users because of gravity flow • Water available when needed: spring and summer months

20. WHY MOUNTAINS ARE WATER TOWERS

21. Precipitation Amount Increases with Elevation Chemical loading also increases with elevation Great Plains Loch Vale Transect from plains to ROMO

22. Percentage of Snow as Precipitation Increases with Elevation

23. More snow stored longer at high-elevation

24. Less ET with Higher Elevations • Trees intercept snow • Less snow reaches ground • High ET loses in both winter and summer for forested areas • Less tress with higher elevations • Colder air temps with higher elevations

25. Drip Irrigation System • Melting snow is similar to a drip-irrigation system • Snow melts slowly and steadily • Snow melt generally stops at night • Maximum infiltration occurs • Little overland flow, flooding, or sediment transport

26. Less Subsurface Storage A higher percent of snowmelt converted to streamflow with increasing elevation, because less subsurface storage to fill

27. Don’t Eat the Snow! • Snowmelt runoff has the best water quality • Snow generally has much less solutes than any streamwater • Snow generally has little anthropogenic contamination

36. Alps case study • Precip doubles • ET: little change • Runoff: 4x greater With mountains No mountains Adapted from Baumgartner et al., in press

37. Climate Change and Mountain Runoff

38. Larger temp increases in mountains Mean change in temperature for 2xCO2 runs from 7 climate models. Black triangles are high mountains for that latitude. White line connects the highest elevations in each grid cell. North American summer months. Note that the climate models suggest increasing temperature change with increasing elevation (Bradley et al., 2004, GRLs).

39. Albedo of Snow • Highest values on earth • Why you get sunburn twice when skiing • Why you sunburn weird places (ears, inside nose) • Lack of snow decreases albedo • Increases warming • Positive feedback • Threshold effect • Very sensitive to climate changes

40. Snowline sensitive to 0oc Isotherm

42. Less Snow, Earlier Melt CIG (www.cses.washington.edu/ cig/figures)

43. Climate-Snow Feedbacks • Amount of snow stored in mountain areas changes dramatically with just a small change in temperature • A small change in snow-covered area results in a large decrease in albedo • More snow melts • Albedo decreases • Positive cycle run amuck • Less total discharge (more ET loss) • Earlier discharge peak • Less summer discharge

44. Western US 1950-2000 SNOWPACK STREAMFLOW (Mote and others) (Stewart and others)

45. Problems with Hydroelectric Power • In the past two decades, the amount of power that Idaho Power Co. has generated cheaply from its 17 hydroelectric dams on the Snake River has dropped. • A drop in July-to-September streamflows, as predicted in the climate models, would reduce power production by 10 to 15 percent, according to the Climate Impacts Group. • Since summer is a peak period for power, the wholesale rates could be high. Idaho Power is allowed to pass on its annual power costs to its 423,000 customers so electricity bills would rise.

46. Glacial Retreat: South Cascade Snow line and glacial extent moving uphill

47. Global Problem Mark Dyurgerov, INSTAAR

48. Global warming threatens ski resorts * 16:25 02 December 2003 * NewScientist.com news service * Duncan Graham-Rowe Hundreds of ski resorts will go out of business because of global warming, according to research published by the United Nations Environment Program on Tuesday.

49. Ski Areas in a Changing Climate • Great uncertainty of future patterns • Low elevation ski areas at risk • Risk of shortened seasons from early & late rains (winter & spring holidays=$$$$) • Number one ski day is Saturday after Thanksgiving • Too warm to make snow?

50. Climate Related Stresses on Ski Area Operations Increased Snowmaking to maintain length of season Increased pressure for year-round operations to offset reduced winter revenues Increased value of shrinking alpine ecosystems might limit expansion Warmer temperatures could make skiing mor enjoyable… From the Proceedings of the Rocky Mountain / Great Basin Regional Climate-Change Workshop