Consumptive Water Use Analysis of Upper Rio Grande Basin in

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Consumptive Water Use Analysis of Upper Rio Grande Basin in Southern Colorado Jonathan Dubinsky, and Arunprakash T Karunanithi Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b01711 • Publication Date (Web): 10 Nov 2016 Downloaded from http://pubs.acs.org on November 16, 2016

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Environmental Science & Technology

Consumptive Water Use Analysis of Upper Rio Grande Basin in Southern Colorado Jonathan Dubinsky and Arunprakash T. Karunanithi* Center for Sustainable Infrastructure Systems, University of Colorado Denver, Denver, CO- 80217, USA *1200 Larimer Street, Denver, CO 80217. Phone: 303-556-2370 Fax: 303-556-2368 email: [email protected]

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Abstract

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Water resource management and governance at the river basin scale is critical for the

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sustainable development of rural agrarian systems in the West. This research applies a

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consumptive water use analysis, inspired by the Water Footprint methodology, to the

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Upper Rio Grande Basin (RGB) in south central Colorado. The region is characterized by

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water stress, extended drought, declining land health, and a depleting water table. We

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utilize region specific data and models to analyze the consumptive water use of RGB.

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The study reveals that, on an average, RGB experiences three months of water shortage

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per year due to the unsustainable extraction of ground water (GW). Our results show that

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agriculture accounts for 77% of overall water consumption and it relies heavily on an

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aquifer (about 50% of agricultural consumption) that is being depleted over time. We find

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that, even though potato cultivation provides the most efficient conversion of ground

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water resources into economic value (m3 GW/$) in this region, it relies predominantly

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(81%) on the aquifer for its water demand. However, cattle, another important

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agricultural commodity grown in the region, provide good economic value but also relies

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significantly less on the aquifer (30%) for water needs. The results from this paper are

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timely to the RGB community, which is currently in the process of developing strategies 1 ACS Paragon Plus Environment


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for sustainable water management.

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Introduction

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Water and energy constitutes two of the most important resource use issues of the century

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as there are limits to the extent that humanity can continue to increase its appropriation of

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fossil fuel resources and freshwater from the natural environment1. Further, water and

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energy interdependencies and supply constraints have been recognized by researchers to

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pose significant risks that can potentially and unintentionally shift overall impacts

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geographically and temporally

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resources needed for the environment as well as human made products (e.g. agricultural

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produce) and processes (e.g. power plant cooling) across nations and sub-regions is the

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necessary first step towards addressing water use issues2,3.

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an approach that provides a useful framework to quantify fresh water usage along the

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entire supply chain5. WF has been previously used to assess both direct consumptive

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water use and indirect embodied water content of individual products such as milk and

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clothes6, as well as to assess entire nations and the global system as a whole8,9. However,

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this paper, which pulls certain concepts from WF, focusses only on consumptive water

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use of a regional system with an aim to provide data and analysis for both the river basin

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water users and water managers10–13. . Note that this analysis is based on water

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consumption as opposed to the more conventional water withdrawal metric, in that a

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consumptive water use metric recognizes the interconnectedness of the hydrologic cycle

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and appropriately allocates evaporation, return flows, irrigation inefficiencies, and other

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withdrawn but “unused” water3.

2,4

. In this context, proper quantification of fresh water

2 ACS Paragon Plus Environment

Water Footprint (WF) 3,6,7 is

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The San Luis Valley (SLV) or Upper Rio Grande Basin (referred to in this research as

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RGB), is a high altitude agricultural valley in South Central Colorado that covers roughly

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21,000 km2 (8,000 square miles). It has an average elevation at the valley floor of 2,300

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m (7,600 ft.) above sea level with an average annual precipitation of 222 mm (9 in). It is

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a snowmelt driven system, with the majority of the water supply coming from river and

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stream flows from the surrounding mountain ranges. Hay production and pasturelands

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utilize some of the snowmelt while much of it flows into the massive aquifer that

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underlies the entire valley, a portion of which is pumped back for irrigation. It is also

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important to note that not all of the water that flows into the RGB is “owned” by the

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region. Two major interstate compacts, the Rio Grande Compact (1938)15 and the

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Amended Costilla Creek Compact (1963)14,, require the SLV to allocate water to

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downstream states based on the annual snowmelt. Along with its unique climate and soil,

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this precious water supply in this high desert region is what allows the SLV to be the

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nation’s second largest region for potato cultivation, the producer of the country’s most

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nutrient rich alfalfa, and the first place in North America to grow quinoa. Barley is

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another important crop grown here and SLV is the main supplier to Coors Brewing

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Company. Because of SLV’s limited population, isolated location, and the fact that its

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natural watershed boundaries coincide closely with its political boundaries resulted in

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EPA considering this region as an ideal study area for regional sustainability analysis16–18

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The impacts of ground water pumping on surface water flows in the region have been

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recognized and the extreme drought of 2002 brought the situation to a head. A robust

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ground water11 model, developed by CDWR, shows that continuous and increasing

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depletion of the aquifer (as monitored since the late 1970s by Davis Engineering (see 3 ACS Paragon Plus Environment


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Figure 1)) has affected surface water flows over the last ten years and impacted

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agriculture which relies on those flows. This region specific model provides a complete

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water balance and paints a picture of consumptive water use in the region that includes

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return flows, crop shortages, and native vegetation22. As agriculture is the major

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economic activity in the region, the community has recognized the importance of

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working towards sustainable management of the region’s water resources on which its

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economy relies heavily19. Due to it’s farsighted and proactive nature, the local

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community demanded legislation from the state that requires sustainable water

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management, namely Senate Bill 04-22220 signed in 2004, which is currently being

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implemented. As part of this bill, the Colorado Division of Water Resources (CDWR)

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has promulgated well rules and regulations and submitted them to the Colorado Water

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Court in the Fall of 201521. The purpose of this legislation is to ensure that the Colorado

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water law priority system is upheld, given the now apparent impacts of ground water

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pumping on surface water flows. Colorado uses the “first in time first in right” prior

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appropriation system of water law, which appropriates surface water rights to the first

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person to divert the water for beneficial use. The RGB’s surface water was fully

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appropriated by 1900, but as ground water at that time was thought to be delinked from

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the surface water system, the state continued to issue well permits for ground water

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pumping until the 1970s. The new legislation requires repayment of injurious depletions

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of senior surface water rights from ground water pumping.

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Another major component of the well rules and regulations, and in some regard the most

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interesting due to the major drop in the aquifer levels that took place during the 2002

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drought, is the requirement that the confined aquifer be maintained at the average historic 4 ACS Paragon Plus Environment

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levels similar to the time period of 1978 to 2000. This is the first legislation of its kind in

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the country and may set a precedent for future sustainable aquifer management

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legislations. The State Engineer’s Office and the CDWR’s Division 3 Engineer, who

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administers the Rio Grande Basin, is responsible for managing and enforcing the ground

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water rules. Also allowed under the legislation is the formation of ground water

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management sub-districts of the Rio Grande Water Conservation District (RGWCD).

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These entities are tasked with managing their water use, replacing injurious depletions to

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the senior surface water rights holders through replacement water, financial water saving

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incentive programs, and restoring and maintaining a sustainable aquifer within the

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parameters of the legislation21.

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Figure 1 Unconfined aquifer level in the RGB over time.

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Simultaneously, Governor John Hickenlooper issued an Executive Order in 2013

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requiring the Colorado Water Conservation Board (CWCB) to develop a statewide water

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plan. Each of the state’s nine river basins, including RGB, was to develop their own

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Basin Implementation Plans (BIP). The Rio Grande Basin Roundtable (RGBRT), by

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involving all major stakeholders and water users, developed a comprehensive BIP (Rio

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Grande Basin Implementation Plan-RGBIP23) that lays out projects, goals, and priorities

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for the basins future. The RGBIP, which was completed and published in the summer of

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2015, is focused on achieving a balance of competing water needs through cooperative

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management of water resources23. The RGBIP outlines detailed plans and allocated funds

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for improving soil health to increase water holding capacity, improving stream flow 6 ACS Paragon Plus Environment

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forecasting, irrigation improvements, head gate and ditch restoration projects, and the Rio

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Grande headwaters restoration project. It also emphasizes the importance of maintaining

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a healthy stream corridor to achieve efficient compact deliveries at the state line. The

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BIPs from across the state, which each focused on their individual basins, informed the

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Colorado Water Plan, which was delivered to the Governor in November of 2015 and

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will highly influence water use in the state (www.Coloradowaterplan.org). This unique

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regional context of freshwater scarcity necessitates development of SLV specific

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methods, models and data to understand and address the problem. In an attempt to fill

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information and data gaps, we present a robust and descriptive, region-specific baseline

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consumptive water use analysis (CWU) that will be available as a resource to assist local

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decision makers who are continuing to develop plans and implement actions towards

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sustainable water use in the RGB.

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Methods

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Our analysis utilizes the concept of tracking the origin (source) of water be it effective

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rain (green) or rivers and streams (blue)

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blue water into surface and ground water components due to the unique hydrologic

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features of the SLV region. We characterize the water consumption in SLV into the

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following three categories: Crops, Livestock, and Municipal / Industrial use; and we

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consider the following three water sources: effective precipitation (green), blue surface

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water runoff (surface/snowmelt), and blue ground water from the aquifer (ground) (see

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Supplemental Information Table S1). The grey water component, which represents water

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needs for pollutant discharge and dilution, was not considered in this study due to lack of

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region specific data and interest. Since this research focuses on the water consumption

24,25

. In the present study, we also divided the



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patterns of the region itself, we only considered water originating within the basin and

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did not account for any upstream-embodied water of imported goods and services. In this

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way, the analysis is different from the traditional Water Footprint methodology.

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The consumptive water use (CWU) calculations adapted for the RGB are shown below:

=

+

150

=

_ +

_ 151 = + 152 = _ + _ + _& 153 = _ + _ + _& 154 155 156

A unique aspect of the presented regional consumptive water use assessment is that we

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first estimate the total consumptive water use in the basin using a local ground water

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model, and then we derive the Consumptive Water Content (CWC) of each crop from

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this overall CWU making the results highly specific to the region. The CWC represents

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the quantity of water needed to produce an unit of a good or service3,26. This level of

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regional specificity was possible due to the close collaboration of our research team with

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the Colorado Division of Water Resources (CDWR), and the use of regional data from

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CDWR’s central database (HydroBase) that houses real-time, historic, and geographic

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data related to water resources in Colorado. By using Rio Grande Decision Support

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System (RGDSS) ground water model22,27, which is specifically calibrated for this region,

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we were able to develop a robust, region-specific accounting that does not rely on global

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averages (which is typical of consumptive water use studies). 8 ACS Paragon Plus Environment

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Crop Water Use of RGB

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The crop water consumption calculations were performed within the Colorado crop

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consumptive water use model (StateCU) component of the RGDSS and considered the

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entire Water Division 328. StateCU, as applied in the RGDSS, models the water budget

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of a ditch service area by calculating the quantity of water consumed by different crops

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using a modified Blaney-Criddle method with locally calibrated crop coefficients. In

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addition, local data related to temperature, precipitation, rooting depths, growing season

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starting and end dates, available water content of soils, irrigated acres, cropping patterns,

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surface and ground water diversions, ditch conveyance and irrigation application

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efficiencies were supplied as inputs into the StateCU model. The data was developed and

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maintained within HydroBase22 as part of the RGDSS efforts.

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We assessed the four major crops cultivated in the region: alfalfa, potatoes, small grains

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(mainly barley) and meadows/pasture grass on a monthly time step from years 2000 to

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2010. They were assessed for potential evapotranspiration, effective precipitation (EF),

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and the remaining irrigation water requirement (IWR). Figure 2 shows a map of the

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irrigated land acreage of various crops.



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Figure 2 - The total acreage and production in the SLV averaged from 2000-2010.

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Much like the global CROPWAT model, which many studies use to estimate crop water

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consumption, the StateCU model is used to estimate the effective precipitation and the

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amount of irrigation water consumed by the crops 6,10,11. Using a local consumptive water

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use model (StateCU) coupled with a local ground water model (RGDSS) is unique and

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critical in that there may be times when precipitation and irrigation water supplies are

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insufficient to meet the entire crop demands, and for these instances there is a shortage

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that may be met if the groundwater table is within the crop’s root zone. The RGDSS

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groundwater model simulates the groundwater table and the associated crop demand

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shortage, and if the groundwater table is within the crop-rooting zone, the groundwater

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model can meet a portion up to the full crop demand shortage through sub irrigation.

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Further, there may be times when all water supplies fall short of meeting the full crop

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demands, which may affect the crop yields. Crop yield data was obtained at the county

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level through the National Agricultural Statistics Service (NASS)29 and are presented in 10 ACS Paragon Plus Environment

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table S2 (see supplementary information).

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Due to the difference in the evaluation methods of this research and StateCU, i.e. this

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research by crop and StateCU by ditch service area, we post processed the StateCU

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results to quantify the individual crop consumptive water use amounts. The analysis

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utilizes information from the Alamosa climate station as an approximation for the

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remainder of Water Division 3 to evaluate crop demands, and then normalizes the crop

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demands back to the Water Division 3 StateCU model results. By combining the post

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processing results from the StateCU model and crop yield data29 we were able to

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determine the CWCgreen, CWCsurface, and in combination with the RGDSS groundwater

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model, the CWCground, for each of the major crops .

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Livestock Water Use of RGB

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We calculated the consumptive water use of livestock (CWUlivetock) in the SLV by

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multiplying the consumptive water content (m3/ton live weight) of a livestock

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(CWClivestock) type by the production quantity in the RGB (See supplementary

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information S3). The three major water uses needed for calculating the CWClivestock are

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drinking water requirement (DWR), service water requirement (SWR), and feed water

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requirement (FWR)10. SWR is a measure of the small amount of water used for keeping

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and maintaining the animals. The DWR and SWR were estimated using global annual

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averages from Mekonnen and Hoekstra’s30 analysis of livestock water footprints for

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grazing animals. In addition, under consumptive water use of livestock we also include

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the water embodied in the feed that the livestock eat (FWR), as this water also originates

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in the basin. The FWR, which accounts for 99% of the grazing livestock CWU, was

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calculated based on local consumptive water content of the feed crops grown in the 11 ACS Paragon Plus Environment


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region (see Supplementary Information table S4) coupled with the amount and feed

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conversion efficiency (FCE) of each type of feed consumed by the livestock. FCE is a

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measure of the quantity of feed needed to produce a certain quantity of output. ! = Σ # ∗ %

227 & = &''( )*+' 228 # =

,-. /01' 23042/ 5'06ℎ)

229 ,-. = (8* 42))'8 03)29' 230 231

A daily dry matter intake (DMI) of 3% of the body weight for adult cattle and 1.5% for

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calves and grazing sheep in accordance with Mekonnen and Hoekstra30 and confirmed by

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the local extension office and a local rancher was used31,32. The total forage consumption

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values were based on the assumption that all feed requirements needed by the livestock

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were satisfied through local resources, as is the practice in the region. The public grazing

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lands in the region has the capacity to support the herd of cattle and sheep spending 3

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months of the year on dry land pasture33–35, 5 months grazing on private irrigated pasture

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and meadows, and 4 months eating baled hay grass and/or hay alfalfa31,32. The total

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livestock headcount was obtained from NASS and since the FWR of hogs originate from

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outside the region, and their population is insignificant (see supplementary information

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table S3), they were not included in this study. Typically, ranchers in the SLV do not

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finish cattle or sheep locally but tend to export live animals; therefore, we used ton live

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animal as the unit for livestock production instead of the more conventional unit of kg

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meat.


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Municipal and Industrial Water Use of RGB

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We calculated the consumptive water use of the municipal and industrial sector

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(CWUM&I) based on input data used in the RGDSS groundwater model on a monthly time

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step for the period of 2000 through 2010. The value for M&I water consumption was

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based on the total pumping and return flows for all non-irrigation high capacity wells

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within the RGDSS model domain, which covers the entire region. In addition to ground

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water pumping, this sector also includes consumptive water use from reservoir

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evaporation of surface water. It is important to note that the manufacturing and industrial

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sector in the SLV represents only ~1% of the overall economy 19.

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Results and Discussion

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Total Consumptive Water Use of RGB

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An examination of the results shows that RGB’s consumptive water use is entirely

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dominated by agricultural activities. Crops account for 63% of the CWU of the valley,

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followed by livestock at 13% and municipal and industrial use accounting for only 3%. In

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addition, native vegetation accounts for about 21% of the overall consumptive water use

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in the valley (Figure 3). The total consumptive water use (in million m3) was divided into

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green water, surface water, and ground water (See Figure 3). By breaking up the blue

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water CWU (CWUblue) into two components: CWUground and CWUsurface, we were able to

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analyze, in fine detail, how the various water users draw upon specific water sources

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(ground vs surface water).



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Figure 3 - Average annual water allocation in the SLV from 2000-2010. (1 Ac-ft. = 1233.5 m3)

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Figure 3 shows that alfalfa is the largest overall user of water followed by meadows and

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pasture and then cattle. It is important to note that meadows and pasture are useful for

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much more than just grazing cattle, as proven by the fact that even after allocating the

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water needed for raising forage for cattle and sheep, the remaining meadows are still one

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of the largest overall contributor to the CWU in the RGB. This apparent over allocation

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of water is due in part to the fact that the majority of irrigation water used for meadows

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and pasture is surface water that is diverted for agricultural uses during early spring and

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summer, in accordance with prior appropriation system. In many locations, the surface

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water is diverted from the rivers or streams across the fields to grow grass where ranchers

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graze their cattle, put up hay for the winter, and export haylage. In addition to providing


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grazing land, meadows also sustain a vast and complex network of wetlands, native

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habitat and species.

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Crop Consumptive Water Use of RGB

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Figure 4 shows the breakdown of the total consumptive water use of crops (CWUcrops) in

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the RGB as well as the CWC for each major crop. This figure should be read inside-out

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with water demand by source type shown in the inner ring and the different crops

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demanding that type of water represented in the outer ring. Overall, 57% of the crop

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water requirement is met by ground water, 27% is met by surface water, and 16% is from

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effective precipitation during the growing season. These results indicate that alfalfa is the

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largest consumer of ground water in the valley while meadows/pasture is the largest

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consumer of surface and green water. The Blue Water Portion (BWP), which combines

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surface water and groundwater needed for all crops in the valley accounts for about 85%

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of the CWUcrops. This BWP for crops in the valley is much higher than the global

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average of 19%26, indicating that the region is much more reliant on irrigation in

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comparison to other regions. In addition, our finding that 57% of the CWUcrops comes

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from ground water resources has a profound and direct bearing on the long term

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sustainability of the aquifer (a key requirement of the new Well Rules and Regulations).



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Figure 4 - The crop water use allocated between CWUgreen-crops, CWUsurface-crops, and CWUground-crops as well as the virtual water content of each crop.

300 301

Livestock Consumptive Water Use of RGB

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The livestock consumptive water use considers water needed for feed crops, drinking

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water, and service water. In the RGB, 98% of the water needs for livestock can be

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attributed to the feed water requirements (FWR). Figure 5 presents a breakdown of the 16 ACS Paragon Plus Environment

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CWUgreen-livestock, CWUground-livestock and CWUsurface-livestock in the Valley. Overall, 40% of

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the livestock water needs are met by green water, 30% by ground and surface water.

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Livestock are able to utilize the sparse green water that falls in the region through dry

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land pasture grazing in the summer months. This, along with meadows and pasture

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grazing, is why we see such a large green water percentage for the livestock CWU. The

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majority of the surface and ground water portion of the CWUlivestock goes to raising

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irrigated pasture for grazing and winter hay feed.

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Figure 5 - Livestock consumptive water use (CWUlivestock) for SLV allocated between CWUgreen-crops, CWUsurface-crops, and CWUground-crops as well as the consumptive water use content of each crop. The smaller pie graph shows that cattle in dominate livestock in the region.

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Agricultural Products

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Table 1 compares the CWC, Total CWU, and water source percentages for each of the

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major agricultural products in the region. Further, we define the ground water intensity as

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a measure of the quantity of ground water needed per ton or per dollar revenue of

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agricultural products. The dollar value for agricultural products sold in Colorado was

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obtained from the USDA29 using the previous 5-year average and was used to calculate

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the ground water intensity measured in $/m3 (see supplementary information table S3 and

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S4)

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The results indicate that, when we use revenue as the index, potatoes have the highest

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efficiency in converting ground water into dollars followed by sheep and cattle. Efficient

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conversion of ground water resources to dollars is not the only measure to determine

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what is best for the region, but it does capture two major issues related to the valley,

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economy and a depleting aquifer. Potatoes are efficient at producing high yields (17 tons

330

/ acres) and hence have a low ground water use per dollar revenue. However, this is offset

331

significantly by the fact that they require the highest ground water portion (81%) per ton

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of crop (see Table 1). This is in contrast to sheep and cattle, which are second in efficient

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conversion of ground water resources into dollars but also have the lowest ground water

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portion (~30%) per ton of any of the agricultural products in the region. Further, the

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current consumption of blue water for crops and livestock (almost all of which is

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exported) results in a net displacement of 1,120 million m3/year (908 thousand ac-ft.) in


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the form of virtual water flows (calculated as area under the ‘blue water CWU crops and

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feed’ curve of Figure 6) of surface and ground water.

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Table 1 - Comparison of major agricultural products in the region from multiple perspectives. (1 Ac-ft. = 1233.5 m3)

Alfalfa Potatoes Small Grains Live Cattle Live Sheep

CWU Content - SLV (m3 t-1) 871.2 100.4 758.5 9529.9 6535.4

CWU Valley Wide (Million m3) 417.5 124.3 200.8 237.6 5.9

Surface Water Portion (SWP) % 23.1 4.5 13.7 30.6 30.1

Ground Water Portion (GRD-WP) % 61.3 81.7 74.1 29.8 30.4

Green Water Portion (GRD-WP) % 15.5 13.9 12.2 39.7 39.5

Ground Water Use / $ Revenue (m3 GW $-1) 2.61 0.41 2.26 1.69 1.54

342 343 344

Blue Water Scarcity

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We use Blue Water Scarcity (BWS)

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the region.

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(WAblue) (See Figure 6).

3,10

as a metric to understand water sustainability of

BWS occurs anytime the WFblue exceeds the Blue Water Availability

: = !;3

Consumptive Water Use Analysis of Upper Rio Grande Basin in

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