For Want of Food: Groundwater and Agriculture

Transcription

1 For Want of Food: Groundwater and Agriculture Outline Thomas Harter University of California, Davis groundwater.org Image: Adam Hart-Davis, 2006 Global water and groundwater use Role of groundwater in agriculture, especially global food production Current and future challenges to groundwater in ag/rural areas Total Water Use Map 100 km 3 = 80 MAF CA: 55 Global Use: 4,000 km 3 3,200 MAF +6,400 km 3 +5,100 MAF from rain to ag Timm Sauer et al., WRR, 10 June 2010: The complex interdependencies between water resources and food production. an evolving global food crisis modified from: United Nations World Water Development Report, 2009 Largest Water Users India China Largest United States Groundwater Users Pakistan (80% of global) Japan India Thailand China Indonesia United States Bangladesh Iran Mexico Bangladesh Russian Federation Pakistan Groundwater Connection to Food: USE OF GROUNDWATER Water Use And % Share of Groundwater-Irrigated Area (km 3 ) 46% 16% 53% Asia: 30% US: 42% CA: 30%-60% 20% 50% modified from: United Nations World Water Development Report, 2009 Groundwater Irrigated Area Data are from: Shah, Villholth, Burke, Groundwater: a global assessment of scale and significance, IWMI, 2007

2 km 3 MAF Trends in Groundwater Use Groundwater for Irrigation Total irrigated area: 1,200 Mac/480 Mha from: Shah et al, 2007 GW irrigated area: 320 Mac/130 Mha IWMI, 2007 CA: km 3 / MAF UN World Water Development Report II, 2006 from: United Nations World Water Development Report, 2009 Shah, Villholth, Burke, Groundwater: a global assessment of scale and significance, IWMI, 2007 Climate Type and GW Use Centers Groundwater Recharge & Major GW Use in Agriculture from: United Nations World Water Development Report, 2009; Shah, Villholth, and Burke, 2007 Total precip on land: 100,000 km 3 (90,000 MAF) Evaporative returns: 67% of precip Renewable supply: 29,000 km 3 (23,000 MAF) Total applied water use: 4,000 km 3 (3,200 MAF) =>Irrigated ag applied water: 2,800 km 3 (2,200 MAF) Irrigated ag ET: 1,550 km 3 from AW, 650 km 3 from rain Groundwater in ag: ~1,000 km 3 (800 MAF) Total rainfed ag water use: 6,400 km 3 (5,100 MAF) Total groundwater recharge: 2,200 km 3 (1,800 MAF) Global Fraction of Cropland Relative to GW Pumping Centers, 1992 Population Map of the World & Major GW Withdrawal Centers CA: 14% of US crop, 7.5% of US livestock $100 billion economic value $36 billion farm cash receipts 81,500 farms and ranches 400 commodities nearly half of U.S.-grown fruits, nuts and vegetables major groundwater users Ramankutty N and Foley JA (1999) Estimating historical changes in global land cover: Croplands from 1700 to Global Biogeochemical Cycles, 13, Modified with world population map from: Nature 439, 800 (16 February 2006) doi: /439800a

3 World Population 20 th Largest Countries by Population UN, World Population Growth to , UN, World Population Growth to , 2004 IPCC, Fourth Assessment Report, 2007, Workgroup III Per Capita Meat Consumption Water Use Per Capita Grain Demand (driven by feed) from: IWMI, Comp Assess. Water Thomas Mgmt Harter, in University Ag, of California, 2007Davis, 2010 Land Use from: IWMI, Comp Assess. Water Mgmt in Ag, 2007 INDIA Challenges to Meeting the Groundwater Needs for Global Food Security GRACE averaging function. M Rodell et al. Nature 460, (2009) doi: /nature08238 Groundwater Storage Loss 18 km 3 /yr 450,000 km 2 area 0.3m/yr water level decline 1.7 km3/yr (1.3MAF/yr) (satellite & USGS Model) 110,000 km 2 area Large annual fluctuations During drought: up to 6m/yr water level decline 10 km 3 /yr (0.8 MAF/yr) 450,000 km 2 area Average decline: 0.1m/yr some areas: few m/yr decline HIGH PLAINS AQUIFER, USA M Rodell and Famiglietti, J. Hydrol 263: Additional Groundwater Demands: Biofuels from: United Nations World Water Development Report, 2009 Global: 10% of energy from biomass (4/5 from wood, dung, crop residue) Global: 5% of biomass production for liquid fuel => 2% of transport energy; Biofuels: : Brazil (54% of all sugar cane) and U.S. (23% of all corn) => 77% of global market in 2007 Only sugar cane has better GHG footprint than fossil fuels Total irrigation water use for biofuels: Currently 44 km 3 (35 MAF), 3% in U.S., 2% in China 225 km 3 (180 MAF) after implementation of current national policies (and d 30M ha (75M acres) additional landuse)

4 Water and Energy from: United Nations World Water Development Report, 2009 Climate Change: Change in GW Recharge From: Döll and Flörke, 2005 In: IPCC 4 th Assessment Report; Salt water intrusion (coastal areas) Changes in ET Change in safe yield: Less recharge from streams in arid and semi-arid regions Change in diffuse recharge from precip More extreme events, including droughts => more reliance on groundwater (savings account) Groundwater Connection to Food: IMPACT 1. Groundwater Salinization Example: Eastern San Joaquin Valley Groundwater Connection to Food: IMPACT 2. Nitrate in Groundwater EC-Field [us/cm] Public Supply Wells (USGS GAMA) 49 Hilmar Domestic Wells (1986, 2001 no trend) 4 Modesto Dairy Domestic Wells (2008) 20 Flowpath & Monitor Wells Non-Dairy Ag Landuse (USGS GAMA) Mean Mean±SE Mean±SD Original GAMA data from Table 1 and 4 in: Upland Modesto Merced Turlock Upland Modesto Merced Turlock Landon and Belitz, Ground-Water Quality Data in the Central Eastside San Joaquin Basin 2006: Results from the California GAMA Program, USGS Data Series 325. Note: 10 mg N/l = 10 kg N/km 2 /yr for each 1 mm/yr recharge UN World Water Development Report II, 2006 N Balance in Three Corn Systems Kenya North China Midwest US Groundwater Loading from Animal Agriculture with Manure Reuse in Intense Feed Crops Vitousek et al., Science, 2009

5 Impact : Nitrate in California Domestic/Municipal Wells Future Impacts Likely Increase: Delay of Impact due to GW Age Age at 100 ft (30 m) depth Age at 300 ft (100 m) depth Harter et al., 2009 Ways out of a Global Food Crisis Improvements in water storage (reservoirs, groundwater banking) and delivery efficiency Improvements in ag water productivity through new breeding / genetically modified crops Drought and salt (!!) tolerance Higher yield Desalination (brackish water, seawater, water reuse in farming and urban areas) Liberate water as a free market commodity & include externalities / supply & demand Future Challenges to Food Supply & Water Around the Globe Decelerating agricultural productivity growth (ultimately due to biophysical limits [Beadle[ and Long, 1985; Bugbee and Salisbury, 1988]) Physical limits to crop land expansion (current reserves mostly in Africa, S.America) Conflicting demands to landuse & water use [Bouwer[ Bouwer,, 2000; Rosegrant et al., 2002,, Hightower & Pierce, 2008] Urban vs. industrial vs. agricultural vs. energy Within ag: : Food vs. feed vs. fiber vs. (bio)fuel( Declining soil quality (e.g., tropical soils) [Foley[ et al., 2005; Ramankutty et al., 2002] Constrains to ag intensification due to environmental and human health regulations [Rockstroem[ et al., 2004; Tilman et al., 2001; Van Hofwegen,, 2006]. => nitrate, pesticides, salts, pharmaceuticals, pathogen contamination of groundwater Climate change => agricultural productivity change Groundwater Resources: Challenges around the Globe Urban/Domestic/Industrial Activities Overdraft in most productive ag regions (e.g., CA, High Plains, NW India, North China Plain) Increased food, feed & biofuel demands => expanded water use Increased pumping cost (due to overdraft) Energy requirements (e.g., India) Compromise to future water security in fossil gw use areas (Middle East/North Africa) Degradation of groundwater Salinization Nutrients, pesticides Emerging contaminants? Impact to wetlands, streams, downstream users Competition with urban water users, environmental water needs Climate Change Energy Sector IMPACT Natural Resources Agriculture Groundwater Ecosystems Surface Water USE Modified from: Shah, Villholth, Burke, Groundwater: a global assessment of scale and significance, Thomas Harter, University IWMI, of California, 2007Davis, 2010

6 Climate Change Ag-Groundwater-Climate Change Salinity Nutrients/Nitrogen Energy Sector Ag-Groundwater-Energy Nexus IMPACT Animal Ag => Pathogens/ Pharmaceuticals Natural Resources Urban/Domestic/Industrial Activities GW Use & Ag-Urban-Ecosystem Interface Environmental Justice Livelihood Agriculture Groundwater GW & Global Food Security Ecosystems Surface Water USE Toward Sustainable GW Use? Controlled increase in gw use in Latin America and Sub-Saharan Saharan Africa to improve rural livelihood Implement effective direct/indirect means to regulate gw withdrawals supply-side side management Artificial recharge, aquifer recovery, rainwater harvesting Wastewater reuse Conjunctive use, groundwater banking, integrated water management Interbasin transfers demand-side management Pricing (energy, water) Legal and regulatory control Water-rights/permits rights/permits Incentives GW Demand Management Irrigation efficiency increase Drought & salt tolerant crops (reuse!) Breeding of crops with higher water productivity Crop diversification: more cash per drop Occupational diversification Improve data base / data collection / monitoring Better understanding of gw supply and demand Public education Modified from: Shah, Villholth, Burke, Groundwater: a global assessment of scale and significance, IWMI, 2007 AGRICULTURE, Ecosystems, & Urban/Industry/Energy Landuse Systems: Homo sapiens Obligate or Facultative groundwater species? Demand (Quantity) Usability (Quality) IMPACT Technical Measures Education Resource evaluation Agricultural management practices Hazard assessment Pollution control Institutional Measures Pollution assessment Water rights Geochemistry Discharge Microbiology regulations Transport / Physics & Geology Landuse Monitoring planning Economic incentives Stakeholder Local/regional Participation planning and management Stakeholder interests Policies GROUNDWATER Quantity Quality USE how obligate exactly how facultative exactly Image: Adam Hart-Davis, 2006