We've all heard, time and again, that California farmers produce about half of this country's fruits and vegetables. The recent drought has focused attention and scrutiny on all aspects of water use in California, including agriculture. The result often plays out as news stories pitting growing urban water needs against farmers who defend their efficiency gains and crucial contribution to the country's food system (here's an example). Implicit in many of these discussions, however, is the idea that taking water away from California farmers necessarily imperils fruit and vegetable production, that a shift of water supply to urban consumers means things like fewer strawberries and tomatoes. Is that really the case though? Where does all of that irrigation water end up?

It turns out California irrigation water is just as likely to end up as cheese on your pizza as it is to be an onion or a watermelon.

In recent history, agricultural activities have accounted for about 80% of the total net water use. The term ‘net water use' commonly refers to the amount of water that is lost from the system – by transport or degradation - as a result of some activity. In agriculture, this includes loss by evapotranspiration (a so-called ‘consumptive' use) or contamination by soil salts.

With so much attention paid to the fruits and vegetables California farmers produce, one might expect the breakdown of agricultural water use in the state to be dominated by those sectors. However, data reported by the California Department of Water Resources (DWR) for 2010 suggest otherwise. 

Pasture: Clover, mixed pasture, native pastures, induced high water table native pasture, miscellaneous grasses, turf farms, bermuda grass, rye grass and klein grass

Fruits: Apples, apricots, cherries, peaches, nectarines, pears, plums, prunes, figs, walnuts and miscellaneous deciduous; Grapefruit, lemons, oranges, dates, avocados, olives, kiwis, jojoba, eucalyptus and miscellaneous subtropical fruit; Table grapes, wine grapes and raisin grapes

Grains: Wheat, barley, oats, miscellaneous grain and hay, and mixed grain and hay; Rice and wild rice; Flax, hops, grain sorghum, sudan, castor beans, miscellaneous fields, sunflowers, hybrid sorghum / sudan, millet and sugar cane; Corn (field and sweet)

Vegetables: Tomatoes for processing & market; Melons, squash and cucumbers; Onions and garlic; Potatoes; Artichokes, asparagus, beans (green), carrots, celery, lettuce, peas, spinach, flowers nursery and tree farms, bush berries, strawberries, peppers, broccoli, cabbage, cauliflower and brussel sprouts

Other: Cotton; Sugar beets; dry beans, safflower

The data show that a large portion of the water evapotranspired by crops – i.e. water consumptively used in the process of growing the crop – goes not to fruits and vegetables but rather to alfalfa, pasture, and grains. In fact, the combined 30% of water used to grow fruits and vegetables is roughly equal to the 28% of water use going to alfalfa and pasture alone.

So if one out of every four gallons of water consumptively used by agriculture in California goes to forages like alfalfa, where do those forages go?

While some California alfalfa does get shipped across the country and even across the Pacific to China, roughly 75% of the alfalfa produced in California stays in the state to feed dairy cattle [1]. The ready supply of high quality forages has been one of the reasons California is now the leading producer of milk in the United States, responsible for ~20% of the national production in 2013 [2]. Increasingly, that raw milk is ending up as cheese, and more often than not that cheese is mozzarella. In 2012 about 43% of raw milk was used for cheese [3]. Mozzarella and ‘other Italian' cheeses accounted for 42% of the cheese produced from that milk. If we assume that all this cheese ends up on pizza and do some back-of-the-envelope calculations based on these estimates*, we se that a little less than 1 in every 100 gallons (0.8 %) used by crops in California ends up going to the cheese on top of your pizza. For reference, that's roughly the same amount that goes to onions, melons, or tomatoes, according to the 2010 DWR data.

This exercise in tracking agricultural water use to consumers is interesting, but doesn't necessarily lead to a meaningful conclusion on its own. Rather, it points to ideas worth contemplating in the context of water use, management and our food. First, the conversion of irrigation water to pizza cheese highlights the ‘virtual water' that gets shipped out of California in various foods and products. Second, and perhaps more importantly, the current agricultural water use configuration in California, at least in aggregate, could accommodate shifts in allocation to different farm and urban sectors without endangering fruit and nut production. Such a shift would rely on reduced alfalfa and/or dairy production, a trend that may already be underway [4,5].

So should California farmers stop growing alfalfa and milking cows? Should water for fruit, nut, and vegetable production have the same priority as cheese? Our water and food systems are complex and interlinked, obscuring any simple answers to these questions and others like them. As impacts from drought and changing climate propagate through California, they are ones people should keep asking.

 *These calculations are greatly simplified and do not take into account any other uses of water along the production chain other than that needed to grow the original alfalfa feedstock.

[1] Putnam D.H., Summers C.G., Orloff S.B.. 2007. Alfalfa Production Systems in California. Publication 8287. Oakland, CA: Division of Agriculture and Natural Resources, University of California.

[2] “USDA Economic Research Service - Dairy Data.” 2015. Accessed March 2. http://www.ers.usda.gov/data-products/dairy-data.aspx.

[3] 2012 Dairy Products Utilization & Production Trends. 2013. American Dairy Products Institute.

[4] “California Dairies Look to Midwest's Greener Pastures | Harvest Public Media.” 2015. Accessed March 2. http://harvestpublicmedia.org/article/california-dairies-look- midwest%E2%80%99s-greener-pastures.

[5] Harrington, Lisa M. B., Max Lu, and David E. Kromm. 2010. “Milking the Plains: Movement of Large Dairy Operations into Southwestern Kansas.” The Geographical Review 100 (4): 538.

When did you first learn about climate change?

UC Davis students demonstrate principles from atmospheric science to an appreciative audience of students and their parents. Courtesy of UC Davis.

With the Next Generation Science Standards (NGSS), students will be introduced to concepts on climate change beginning in middle school. The NGSS was released in 2013 as the new framework for effectively teaching and assessing STEM education, based on scientific research by the National Research Council. The subject areas include the physical sciences, life sciences, earth and space sciences, engineering, technology, and applications of science.

At this time, only 13 states have adopted the NGSS. In other regions, controversy over acceptance of climate change has stalled adoption. However, California adopted the NGSS in September 2013.

Blue depicts states that have adopted Next Generation Science Standards

At UC Davis, the Mathematics and Science Teaching Program team on climate change is currently working on developing teaching modules incorporating these new standards. In working with the team, led by Professor Tessa Hill and Mary-Betty Stevenson, I contributed to the design, content, and execution of climate change lessons targeted to middle school grades.

This spring, middle school students from local schools will be coming to UC Davis to participate in these climate change activities. Groups of students will rotate between modules, which are designed for 25 minutes and can be easily duplicated in the classroom. Designed to be engaging, hands-on activities that introduce students to the concepts of climate change while incorporating skills in math and chemistry, these modules include ocean acidification games, demonstrations on changes in pH using household products, and modeling atmospheric carbon dioxide data. Lesson plans from these activities will be made available for teachers, with the hope that they become widespread.

Let the learning begin!

UC Davis recently profiled CCWAS Trainee Katie Markovich. Check it out!

It seems clear from the last blog post that the optimism inspired by late December rains has now been overshadowed by one of the warmest and driest Januaries on record. This left me wondering what this means for California's ongoing multi year drought? We usually talk about drought in the summer, so how important is January precipitation?

Short answer: really important.

This time of year, water managers are usually paying close attention to the snowpack. Although water demand peaks in the summer months, a significant portion of the water supply actually falls as snow during the winter where it is stored in the snowpack until it melts and runs off into reservoirs in the spring. Snow accumulated in the winter (generally from October to March) provides roughly 1/3 of the total water supply for California. On average, this equates to more than 15 million acre feet of water, which is more than all of the water used by CA cities in 2010.

January is typically the wettest month and is an important contributor to the total snowpack. Unfortunately, this year two factors are resulting in below average numbers. First, it's not snowing; this January was the driest on record in many locations. Second, above average temperatures actually melted some of the snow that was accumulated in December. The resulting snowpack totals for January are not encouraging. As of February 2nd, the overall water storage in the snowpack is 22% of normal for this time of year, and only 14% of the average April 1st total (the standard date used for peak snowpack measurements). The picture is even bleaker considering that, given the three consecutive years of drought preceding this one, what we really should be shooting for is wet, not average. 

Based on the current snowpack, the probability of ending the drought this water year seems low. To make up for the current drought deficit, it's estimated that California will need precipitation totals that are 150% of normal by September 30th. To achieve this, the snowfall in February and March will need to be well above average, and current forecasts are not predicting this. The most recent seasonal drought outlook issued by the National Oceanic and Atmospheric Administration (NOAA), shown here, actually predicts that drought will persist or intensify in Northern California.

Given this trajectory, it is likely that another year of drought is probable, if not certain. However, this is not to say that this year can't be better than last. I would like to close with two positive observations. First, the reservoir levels this month are actually slightly better than this time last year. Also, its only the beginning of February, which means that there are still two months left in the snow season for these numbers to improve.