Drought Resilience JAWRA Article

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MILLER, DALE, BRUSH, VICUNA, KADIR, DOGRUL, AND CHUNG TABLE 3. Monthly Change in Surface Water Diversions Compared With Base Period Diversions. Moderate Slight Severe Moderate Slight Drought Drought Drought Drought Month (m/year) ( %) (m/year) ( %) ( m/year) ( %) Oct 65 68 88 Nov 73 73 99 Dec 93 86 118 Jan 32 46 65 Feb 15 19 23 Mar 18 25 30 Apr 65 75 89 May 49 70 81 Jun 61 76 90 Jul 63 81 94 Aug 59 74 86 Sep 50 67 79 Annual 49 61 74 Trend in Ground Water Altitude A Moderate 30 -Year Drought 0 E -5 4r n S -20 e -25 s � -30 E v -3 40 ........ ............................... e°--°- -- °--.......................... 0 vueht P,dO Rec.v.ry 5 0 10 2D 30 : 50 W 70 SIm.LtI.. Y.,r B Trend In Ground Water Altitude Slight 60 -Year Drought TABLE 4. Impact of Simulated Droughts on Surface Water Diversions. periods to make up for declines in surface water deliveries. To maintain constant irrigation levels in the entire Central Valley during the simulated droughts, ground -water pumping increased by 71% in the severe drought, 49% in the moderate drought, and 27% in the slight drought scenario (Table 6). Interestingly, drought period ground -water pumping is greater than the reduction in surface water diver- sions. For example, Central Valley ground -water pumping increases 0.12 m/year (0.36 ft/year) in the severe drought, when surface water diversions declined only 0.11 m/year (0.33 ft/year). Increases in ground -water pumping in the San Joaquin Basin and Tulare Basin range from 0.01 to 0.04 m/year (0.04 to 0.12 ft/year) greater than the reduction in surface water diversions. This increase in ground -water pumping is required to compensate for the reduced precipitation experienced during drought years (Table 2). Indeed, changes in ground -water pumping may be a better indicator of drought severity than changes in surface water diversions in most regions. For example, ground -water pumping in the Eastside Drainage increases by 0.05 m/year (0.16 ft/year) in 5 ................... ..... ..............................- a .......................... Dmueht Perl.tl Recovery 0 -5 .1n -15 -20 .25 -30 -35 •�Ee.tsde � - 7.bre � S.a.mento - S. Joaquin - T.I.re 0 10 20 30 40 50 e0 70 w e0 100 Slmmauon Year Trend In Ground Water Altitude C Severe 60 -Year Drought e u -- 3..remento - � Eesuma +3.e J..,ln � -r.lere slmulati -Y.ar FIGURE 2. Ground -Water Trends Before, During and After (A) a Moderate 30 -Year Drought, (B) a Slight 60 -Year Drought, and (C) a Severe 60 -Year Drought. the severe drought scenario, 0.04 m/year (0.13 ft/year) in the moderate drought scenario, and 0.02 m/year (0.07 ft/year) in the slight drought scenario, while surface water diversions in this region remain close to base period levels (Table 6). JAWRA 862 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION Severe Moderate Slight Hydrologic Base Period Drought Drought Drought Region (kin /year) (km /year) (km (kin /year) Sacramento 4.73 3.44 4.48 5.06 Eastside 0.02 0.01 0.01 0.01 San Joaquin 3.24 1.79 2.62 2.69 Tulare 3.57 1.07 1.37 1.93 Central Valley 13.44 8.20 10.46 11.75 Change( %) 39% 22% 13% periods to make up for declines in surface water deliveries. To maintain constant irrigation levels in the entire Central Valley during the simulated droughts, ground -water pumping increased by 71% in the severe drought, 49% in the moderate drought, and 27% in the slight drought scenario (Table 6). Interestingly, drought period ground -water pumping is greater than the reduction in surface water diver- sions. For example, Central Valley ground -water pumping increases 0.12 m/year (0.36 ft/year) in the severe drought, when surface water diversions declined only 0.11 m/year (0.33 ft/year). Increases in ground -water pumping in the San Joaquin Basin and Tulare Basin range from 0.01 to 0.04 m/year (0.04 to 0.12 ft/year) greater than the reduction in surface water diversions. This increase in ground -water pumping is required to compensate for the reduced precipitation experienced during drought years (Table 2). Indeed, changes in ground -water pumping may be a better indicator of drought severity than changes in surface water diversions in most regions. For example, ground -water pumping in the Eastside Drainage increases by 0.05 m/year (0.16 ft/year) in 5 ................... ..... ..............................- a .......................... Dmueht Perl.tl Recovery 0 -5 .1n -15 -20 .25 -30 -35 •�Ee.tsde � - 7.bre � S.a.mento - S. Joaquin - T.I.re 0 10 20 30 40 50 e0 70 w e0 100 Slmmauon Year Trend In Ground Water Altitude C Severe 60 -Year Drought e u -- 3..remento - � Eesuma +3.e J..,ln � -r.lere slmulati -Y.ar FIGURE 2. Ground -Water Trends Before, During and After (A) a Moderate 30 -Year Drought, (B) a Slight 60 -Year Drought, and (C) a Severe 60 -Year Drought. the severe drought scenario, 0.04 m/year (0.13 ft/year) in the moderate drought scenario, and 0.02 m/year (0.07 ft/year) in the slight drought scenario, while surface water diversions in this region remain close to base period levels (Table 6). JAWRA 862 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION