Continental-scale water resources modeling

Transcription

1 Continental-scale water resources modeling Ingjerd Haddeland and Thomas Skaugen (University of Oslo/Norwegian Water Resources and Energy Directorate) Dennis P. Lettenmaier (University of Washington)

2 Outline Background What, why Approach Model, data Results Conclusions

3 Outline Background What, why Approach Model, data Results Conclusions

4 Introduction Irrigation % of global water withdrawals (Shiklomanov, 1997) >30,000 large dams 20% of global mean annual runoff can be retained in reservoirs (Vörösmarty et al., 1997) 35 % built for irrigation purposes alone (ICOLD, 2003) Freshwater scarcity: one of the most important environmental issues of the 21st century (UNEP, 1999) Vörösmarty and Sahagian, Bioscience, 2000.

5 Irrigation

6 Irrigated areas 150 W 120 W 90 W 60 W 30 E 60 E 90 E 120 E 150 E 60 N 30 N 60 N 30 N Percent irrigated areas > <0.1 Stefan Siebert, Petra Döll, Sebastian Feick and Jippe Hoogeveen (2005), Global map of irrigated areas version 3, Institute of Physical Geography, University of Frankfurt, Germany / Food and Agriculture Organization of the United Nations, Rome, Italy Irrigated areas, globally: 2.8*10 6 km 2 ~2 % of global land area Location of irrigated areas: Asia: 68% America: 16% China, India, USA: 47%

7 Irrigation: Definitions Irrigation water requirements: Water required in addition to water from precipitation (soil moisture) for optimal plant growth during the growing season (Consumptive) irrigation water use: Water, in addition to water from precipitation, actually used by plants. Is equal to, or less, than irrigation water requirements. Irrigation water deficits: Irrigation water requirements Irrigation water use

8 Reservoirs

9 Reservoirs Dam Percent irrigated areas > <0.1 Fraction of all dams Main purpose of dam Irrigation Flood Hydro Irrigation Flood Hydro Fishing Navigation Recreation Water supply Unknown Fishing Navigation Recreation Water supply Unknown ICOLD, World Register of Dams 2003, International Commission on Large Dams (ICOLD), Paris, France.

10 Objectives of this study Model the effects of irrigation and large reservoirs on the water balance, with the objective of obtaining plausible reproductions of observed flows at the outlets of large river basins, with a special emphasis on river basins affected by irrigation. Traditional land surface schemes: Simulates naturalized runoff Model development: Generic reservoir model Irrigation scheme m 3 s ) Columbia J F M A M J J A S O N D Naturalized Observed Percent irrigated > <0.1 Dam

11 Variable Infiltration Capacity model

12 Approach Macroscale hydrologic model: VIC Resolution Spatial: 0.5 degrees Temporal: Daily Input data Precipitation, max/min temperature, wind Land cover data (vegetation, soil properties, topography) Time period: Irrigation scheme VIC. Surface water withdrawals only Reservoir module Routing model Cropland Grasslands Open Shrublands Closed Shrublands Wooded Grasslands Woodland Mixed Cover Deciduous Broadleaf Deciduous Needleleaf Evergreen Broadleaf Evergreen Needleleaf Bare soil/ice Dominant vegetation type Evergreen Needleleaf Evergreen Broadleaf Deciduous Needleleaf Deciduous Broadleaf Mixed Cover Woodland Wooded Grasslands Closed Shrublands Open Shrublands Grasslands Cropland Bare soil/ice Second most dominant vegetation type

13 Irrigation scheme Irrigation starts Irrigation ends Soil moisture Soil moisture Field capacity 0 Wcr 0 10 Time

14 Irrigation scheme Non-irrigated Irrigated

15 Reservoir model 1 st priority: Irrigation water demand 2 nd priority: Flood control 3 rd priority: Hydropower production If no flood, no hydropower: Make streamflow as constant as possible Q i = min 7Q10 River Non-irrigated part of grid cell Irrigated part of grid cell Reservoir Dam Water withdrawal point Water withdrawn from local river Water withdrawn from reservoir Q max i = i min S ( S + Q ) 1 i 1 S ini end, Q Q inday min day= i day= i day= i E res day

16 Validation m 3 /s Columbia, The Dalles 0 J F M A M J J A S O N D Model evaluation: 1) Columbia, 2) Colorado, and 3) Missouri River basins m 3 /s Colorado, Glen Canyon 0 J F M A M J J A S O N D Naturalized streamflow Simulated, no irrigation, no reservoirs Observed streamflow Simulated, irrigation and reservoirs Percent irrigated > <0.1 Dam m 3 /s Missouri, Hermann 0 J F M A M J J A S O N D

17 Results: Irrigation water 120 W 110 W 100 W 90 W 80 W 70 W 50 N a) 40 N 40 N 20 N 30 N 120 W 110 W 100 W 90 W 80 W 70 W 50 N b) 40 N 40 N 20 N 30 N 120 W 110 W 100 W 90 W 80 W 70 W 50 N c) 40 N 40 N 20 N 30 N 40 E 60 E 80 E 100 E 120 E a) 40 E 60 E 80 E 100 E 120 E b) 40 E 60 E 80 E 100 E 120 E c) a) Irrigation water requirements b) Irrigation water uses c) Irrigation water deficits Irrigation water requirements USA+: 18 mm year -1 Asia: 16 mm year -1 Irrigation water uses USA+: 10 mm year -1 Asia: 10 mm year -1 Global terrestrial - precipitation: 800 mm year -1 - evapotr.: 400 mm year mm year -1

18 Results: Streamflow km 3 month -1 fraction a) 790 c) East Pacific J M M J S N Arctic J M M J S N 260 b) d) West Atlantic J M M J S N 220 Indian J M M J S N 630 e) West Pacific J M M J S N 1) No reservoirs, no irrigation 2) Reservoirs and irrigation Dam Percent irrigated areas > <0.1 Effects on freshwater fluxes reaching the oceans. a) and b) represent rivers draining USA to the Pacific and Atlantic Oceans, respectively. c) represents rivers draining northwards to the Arctic Ocean in the Asian region, while d) and e) represent river draining Asia to the Indian and Pacific Oceans, respectively. The lower panels show the results of simulations 2 divided by simulation 1.

19 Colorado River basin Percent irrigated > <0.1 Dam a) Irrigation water requirements b) Evapotranspiration increase c) Changes in latent heat fluxes d) Changes in sensible heat fluxes e) Changes in surface temperatures mm Percent Wm Wm o C Naturalized: Q: 42.3 mm year -1 ET: 335 mm year -1 Irrigation included: Q: 26.5 mm year -1 ET: 350 mm year -1

20 Conclusions The model does a reasonable job of reproducing the effects of management on selected large rivers. Reservoirs and crop irrigation water use has the potential of altering the natural hydrologic water balance of river basins. The effects of land use changes can be significant locally. Averaged over larger regions, the effects are most noticable in the area draining to the Eastern Pacific Ocean.

21 Questions?

22 References Haddeland, I., D.P. Lettenmaier, and T. Skaugen, 2006, Effects of irrigation on the water and energy balances of the Colorado and Mekong River basins, Journal of Hydrology, 324(1-4), Haddeland, I., T. Skaugen, and D.P. Lettenmaier, 2006, Anthropogenic impacts on continental surface water fluxes, Geophysical Research Letters, 33, L08406, doi: /2006gl026047