Global Groundwater Withdrawal

Transcription

1 Global Groundwater Withdrawal Large withdrawals in North India, Western US, Middle East, Spain Global total ~630 km 3 More than 90% is used for irrigation Reported: Wada et al., 010 (IGRAC) Results agree fairly well for many countries Even the reported values may have significant uncertainties as they are reconstructed based on population distribution 4 Irrigation Pumping and Groundwater Depletion Yadu N. Pokhrel, Oki Lab. IIS Slide 9

2 30 Groundwater withdrawal Groundwater withdrawal in major countries Unit: km 3 /yr This study WRI (007) India USA Pakistan Mexico Bangladesh Saudi Arabia Ground water withdrawal in the Ogallala aquifer Unit: mm/yr This study USDA (00) Area km Maize Wheat Cotton (Hanasaki et. al, J. Hydrol., 010)

3 Simulated River Discharge (Highly Regulated Basins) Seasonal variation improves significantly in many regulated basins. R.I. Reservoir capacity/annual flow volume * 100 Representing Human Impacts in MATSIRO Yadu N. Pokhrel, Oki Lab. IIS Slide 31

4 Global Irrigation Water Requirements Simulated net irrigation water requirement: grid averaged values. Representing Human Impacts in MATSIRO Yadu N. Pokhrel, Oki Lab. IIS Slide 3

5 Validation of Irrigation Water Use Observed data: FAO AQUASTAT (country statistics), 1998~00 Water use efficiency: Doll & Siebert (00) Year 000 Year 1987 The model estimates of irrigation water withdrawals agree well with the observations. Error bars: uncertainty due to precipitation data. Representing Human Impacts in MATSIRO Yadu N. Pokhrel, Oki Lab. IIS Slide 33

6 Human Impacts: River Discharge and TWS Storages (Global) Aral Sea Inflow 510 km 3 in 50 years 3 Human Regulation of Terrestrial Water Cycle in the Past Yadu N. Pokhrel, Oki Lab. IIS Slide 34

7 35 Virtual Water Balance in Countries (m 3 /c/y) in 000 Major crops and meat Blue: Exporting Red: Importing (Oki, et. al, 004) Exporting Importing 7 out of top 10 importing countries are seriously poor in water resources. 7 out of top 10 exporting countries are rich in water resources. Denmark (10) and India (18) are water stressed but exporting RW in net.

8 36 World Water Resources Considering Virtual Water Trade Potentially Available Water Resources per Capita in 000 Country base +VW GSWP ensemble runoff, SRES A1/B1 population Seriously Stressed (~1) Stressed (1~) Slightly Stressed Moderate (5~10) Rich (10~) (~5) 10 3 m 3 /capita/year

9 37 Conventional Water Resources Assessment Potentially Available Water Resources per Capita in 000 Country base GSWP ensemble runoff, SRES A1/B1 population Seriously Stressed (~1) Stressed (1~) Slightly Stressed Moderate (5~10) Rich (10~) (~5) 10 3 m 3 /capita/year

10 % 100% 80% 80% Burundi: 31m 3 /c/y 60% 40% 40% 0% 0% 0% 0% Water Resources Assesment Considering VW trade Countries were classified into seriously stressed in 000 by conventional water resources assessment. VW Balance 0 0 Rwanda:53m 3 /c/y Egypt:141m 3 /c/y Virtual Water Import Stressed Poor Countries remain Water Poor Seriously Stressed 3 1 ~ 1, 000 USD 1, 000~ 5, 000 5, 000~ 0, 000 ~ 1, 000 USD 1, 000-5, USD 000 5, 000-0, USD 000 USD USD GDP per capi t a ( US$/y/c) GDP per ca pi t a ( US$/y /c) Slightly Stressed 3 Rich Countries are saved by VW import 6 1 0, 000USD~ 0 0, 000 USD~ UAE:4,490m 3 /c/y Sl iigght ht l yl y St r es s ed St r es s ed Ser i ous Ser i ous Oman: 51m 3 /c/y Bahrain:313m 3 /c/y (Oki, et. al, 004)

11 39 R ws = (W-S)/Q and A wc = Q/C(m 3 /y/c) have similar global distribution Is (W-S)/C globally uniform?

12 40 Virtual Water Import to Japan Other: Total : 64.0km 3 /y.5 Vi r t ual Wat er I mpor t t o Japan t hr oug h each pr oduct s 1, 3 ( k m3/y) Mai z e,, 5 14, 5 3, , 1, 4 9, 4 Soybean Wheat Ri ce Bar l ey Beef Por k Blue+Green water Blue water only (for JFY in 000) (Oki, et. al, 00, IHE-UNESCO) Domestic Withdrawals in Japan: 89 km 3 /y Domestic Blue Water in Japan: 400 km 3 /y Domestic Green Water in Japan: 30 km 3 /y

13 Groundwater Representation 6 more layers of 1m and one of 90 m thickness Koirala (010) Based on Yeh and Eltahir (005a,b) Soil Column has explicit saturated and unsaturated soil zones. Interacting through exchange of moisture flux (GW recharge) GW Recharge is estimated based on Richards equation: Water Balance of GW reservoir: d S I Q t gw y gw gw Baseflow initiates when WTD is shallower than threshold value: Q K d d if 0 d d gw 0 gw gw 0 Q 0 if d d gw gw 0 I gw d k 1 dz Lateral flow between grid cells is not considered S y : Specific yield, I gw - recharge, Q gw is baseflow, d gw - water table depth (WTD), d 0 - threshold WTD, K-outflow constant. 4 Irrigation Pumping and Groundwater Depletion Yadu N. Pokhrel, Oki Lab. IIS Slide 41

14 Groundwater Withdrawal (US Aquifers) High Plains Aquifer (HPL) Simulated withdrawals compare well with USGS observations. Groundwater is mainly used for irrigation. Groundwater contributes ~75% of all water uses in areas overlying the HPL. 4 Irrigation Pumping and Groundwater Depletion Yadu N. Pokhrel, Oki Lab. IIS Slide 4