Water for River Restoration: Potential for Collaboration between Agricultural and Environmental Water Users in the Rio Grande Project Area

Transcription

1 Water for River Restoration: Potential for Collaboration between Agricultural and Environmental Water Users in the Rio Grande Project Area Report prepared for Chihuahuan Desert Program, World Wildlife Fund By: J. Phillip King, P.E., Ph.D. Julie Maitland, M.A. June 2003

2 Table of Contents List of Figures... 4 List of Tables... 5 Acknowledgements... 6 Executive Summary... 7 Chapter I : Introduction A. Objectives B. Scope and Limitations Chapter II : The Rio Grande and its Institutions A. Physiographic Description of Study Area B. The Rio Grande Compact C. The Rio Grande Project Chapter III : Demographics and Socio-Economics for Agriculture A. Number and Size of Farms B. County Profile Information C. Summary of Market Value of Agricultural Products D. Trends and Technology Dairy Production Irrigation Technology Price of Water E. Net Cash Return and Government Payments F. Characteristics of Farm Operators G. Regional Population Information H. Municipal Water Demand Chapter IV : Irrigation Hydrology A. Release, Diversion, Delivery, Losses, and Return Flows B. Efficiency C. Water Conservation Hydrology Chapter V : Elephant Butte Irrigation District A. Background and History B. Organization C. Diversion structures and service area D. Conveyance System E. Farm application F. Drainage and return flow system G. Cropping patterns in EBID H. Transfer policies and procedures I. Non-agricultural water use J. Conservation policies and practices Chapter VI : El Paso County Water Improvement District No A. Background and History B. Organization C. Diversion Structures and Service Area D. Conveyance System E. Farm Application F. Drainage and Return Flows... 81

3 G. Cropping patterns in EPCWID H. Transfer Policies and Procedures I. Non-agricultural Water Use in EPCWID Chapter VII : Hudspeth County Conservation and Reclamation District No A. Background and History B. Organization C. Diversion Structures and Service Area D. Conveyance System E. Farm Application F. Drainage and return Flows G. Cropping patterns in HCCRD H. Potential for Water Conservation for Restoration Chapter VIII : Potential for Managing Water for Restoration Projects A. Developing the Institutional Framework for Obtaining and Managing Water for Restoration B. Purchase of Water Rights C. Leases of Water D. Passive Use of Water for Restoration E. Water Conservation for Restoration F. On-Farm Water Conservation Farm Delivery Metering Laser Leveling Pressurized Irrigation (Drip and Sprinkler) High Flow Turnouts Low Water Use Crops Deficit Irrigation Cultural Practices G. System-Level Conservation Canal Lining Rates and Rate Structures Charges to Constituents Release Management to Maximize System Efficiency Chapter IX : Current Issues on the Rio Grande A. Endangered Species B. New Mexico Stream Adjudication C. Disputes between Texas and New Mexico over the Rio Grande Chapter X : Summary and Conclusions References Appendices A. Compact Disk Rincon.jpg Map of Rincon Valley irrigation system, EBID Mesilla.jpg Map of Mesilla Valley irrigation system, EBID and EPCWID El Paso.jpg Map of El Paso Valley irrigation system, EPCWID Hudspeth.jpg Map of Hudspeth County irrigation system, HCCRD B. The Rio Grande Compact

4 C. The 1906 Convention between the United States and Mexico, Equitable Distribution of the Waters of the Rio Grande D and 1908 Letters from U.S. Reclamation Service to Territorial Engineer of New Mexico appropriating water for the Rio Grande Reclamation Project E. EBID Mutual Water Users Association Policy

5 List of Figures Figure 1: Rio Grande Compact area. From Report of the Rio Grande Compact Commission, Figure 2: Rio Grande Compact index gages. From Report of the Rio Grande Compact Commission, Figure 3: Rio Grande Project map. See included CD for more detailed project maps Figure 4: Deliveries to Mexico at the Acequia Madre and Caballo releases, Figure 5: The D1 and D2 allocation curves Figure 6: Organizational chart for Elephant Butte Irrigation District Figure 7: Percha Diversion Dam Figure 8: Leasburg Diversion Dam (photo by Zhuping Sheng) Figure 9: Mesilla Dam Figure 10: Groundwater well in EBID Figure 11: Seasonal variation in monthly flow and TDS in the West Drain, Figure 12: Annual flow of the West Drain and Westside Canal, Figure 13: Crop mix in EBID, Width of each bar represents irrigated acreage Figure 14: Tentative structure for transfers of water to MWUAs Figure 15: Hydrologic schematic of the Rio Grande between Caballo Dam and Courchesne Bridge (Rio Grande at El Paso gauging station) Figure 16: Flows at Caballo and Courchesne Bridge, and net depletion in reach Figure 17: American Dam and the heading of the American Canal Figure 18: Cropped acreage in EPCWID, , Figure 19: Diversions in EPCWID, Figure 20: Location of Hudspeth County Conservation and Reclamation District No. 1 (from Kirby, 1978) Figure 21: Water supply from EPCWID to HCCRD (from Kirby, 1978) Figure 22: Irrigated acreage, total inflow, and charges to HCCRD Figure 23: Potential structure for Environmental Water Users Association within EBID Figure 24: Riparian vegetation along the Selden Drain, EBID, A beaver dam is in the foreground Figure 25: Center pivot irrigation system (from Zimmatic, inc.) Figure 26: High flow turnout on pecans in EBID Figure 27: Caballo releases in 1956 and

6 List of Tables Table 1: Summary of characteristics of EBID, EPCWID, and HCCRD Table 2: Summary of water conservation potential for river restoration in the Rio Grande Project area Table 3: Conejos River at Mouths (Los Sauces) as a function of Conejos Index Supply. Column numbers (1) and (2) refer to the column designations in the Rio Grande Compact Table 4: Rio Grande at Lobatos as a function of Rio Grande at Del Norte Table 5: Elephant Butte index as a function of flow at Otowi Bridge Table 6: Colorado deliveries to New Mexico, Table 7: New Mexico Deliveries to Texas Table 8: Project Storage and Release accounting, Table 9: Delivery schedule for water to Mexico under the Treaty of Table 10: Sierra County, New Mexico farm and irrigated land data, from Ag. Census, Table 11: Doña Ana County, New Mexico farm and irrigated land data, from Ag. Census, Table 12: El Paso County, Texas farm and irrigated land data, from Ag. Census, Table 13: Hudspeth County, Texas farm and irrigated land data, from Ag. Census, Table 14: Agricultural production by county for study region Table 15: Alfalfa water use and return under flood and trickle irrigation in Doña Ana County, from McGuckin (1991) Table 16: Crop Acreage, Water Use, Net Returns and Average Value per Acre Foot in EBID, from McGuckin Table 17: Crop Acreage, Water Use, Net Returns and Average Value per Acre Foot in EPCWID, from McGuckin Table 18: Net return and government payments to farms (Ag. Census, 1997) Table 19: Demographics of farmers in study area counties, from USDA National Agriculture Statistics Service (1997) Table 20: Population change in study area counties, Table 21: Urban water use in Las Cruces, the City of El Paso, and Ciudad Juarez for 1998 and estimated for 2038, from Paso del Norte Water Task Force, Table 22: Parcel size distribution within EBID, Table 23: EBID flat rate assessments, Table 24: Crop mix acreage in EBID, Table 25: Cropped acreage in EPCWID, and From District records (this omits some very minor crops and does not subtract out double cropped acreage) Table 26: Crops and crop value in HCCRD, , from Blair (2001) Table 27: Water prices in the Western United States, from Business Valuation Services, Table 28: General characteristics of irrigation system types, based on Cuenca (1989) Table 29: Center pivot cost as a function of size Table 30: Summary of potential projects for acquiring water for river restoration

7 Acknowledgements The authors would like to express their sincere gratitude to Jake Kline and Kenneth Carr of Hudspeth County Conservation and Reclamation District No. 1 for their help and hospitality. We would also like to thank Al Blair, consultant to HCCRD and El Paso County Water Improvement District No. 1 for his help in gathering information for this report. Tom McGuckin s work and advice have been very valuable to us. Our understanding of the history, geography, and subtleties of the operation of the Rio Grande Project and HCCRD has been greatly enhanced by Jim Kirby. We thank Gary Esslinger, Henry Magallanez, and James Narvaez of Elephant Butte Irrigation District for their help. We greatly appreciate the input of Gary Arnold, Rudy Provencio, James Salopek, and Mack Sloan, and for their candor in discussions with us on complex issues. Finally, we are most grateful to Beth Bardwell of the WWF for her involvement, help, and especially patience. 6

8 Executive Summary This report, commissioned by the World Wildlife Fund (WWF), examines the potential for developing sources of water for river restoration efforts. The primary geographic focus is the Rio Grand Project, stretching from Elephant Butte Dam in Sierra County, New Mexico, to Fort Quitman in Hudspeth County, Texas. The Rio Grande Project was built to deliver surface water to farmers in Elephant Butte Irrigation District (EBID), El Paso County Water Improvement District No. 1 (EPCWID), and to make deliveries required by treaty to the Republic of Mexico in Ciudad Juarez. Hudspeth County Conservation and Reclamation District No. 1 (HCCRD) uses excess flows leaving EPCWID for irrigation. This report focuses on the opportunities for identifying water that is, or could be made to be available from the three U.S. districts for river restoration projects. The primary source of water for the Rio Grande Project is runoff in the Rio Grande from southern Colorado and northern New Mexico. This water is stored in two reservoirs, Elephant Butte and Caballo. The Rio Grande Compact is a 1938 interstate agreement among Colorado, New Mexico, and Texas that apportions water to the three states and provides water for delivery to Mexico as dictated in a 1906 treaty between the U.S. and Mexico. The Compact places the Rio Grande Project, including EBID which is entirely located in New Mexico, under the administrative authority of the Texas Compact Commissioner. Within the Texas Compact area, water is distributed to Rio Grande Project water users by the Bureau of Reclamation, and managed within the irrigation systems by the respective districts. Originally constructed by the U.S. Bureau of Reclamation around 1916, the Rio Grande Project was operated by Reclamation as a single irrigation system until the districts paid off their federal construction loans in Since that time, the districts have operated as separate management units with their own boards of directors and district personnel. Reclamation continues to operate the storage dams, coordinating releases from storage to meet orders from the districts and Mexico. The diversion structures providing water to the districts are maintained and operated by the districts under contract to Reclamation, who maintains ownership of the diversion structures. The International Boundary and Water Commission (IBWC) maintains much of the river channel in the study reach, including flood control levies and river rectification structures. EBID, the upstream district in the project, provides water to 90,640 water-righted acres in New Mexico. Farmers grow pecans, alfalfa, cotton, vegetables including onions, lettuce, cabbage, and chile, and other forage and miscellaneous crops. There is a general increase in acreage of pecans, and a declining acreage of cotton. Overall actual irrigated acreage has decreased to about 75,000 acres, though the full 90,640 maintains appurtenant water rights. While all of the district s water is currently supplied to irrigators, the district has developed a policy to facilitate conversion of agricultural water to municipal use if and when municipal water providers in the service area develop the capacity to treat surface water. Farmers in EBID supplement their surface water supply with groundwater produced from private wells. One important ongoing activity in EBID is the adjudication of water rights, both surface and ground water, by the New Mexico Office of the State Engineer. EPCWID provides water to 69,010 water-righted acres in Texas. Primary crops are cotton and alfalfa, with some forage, vegetables, and pecans. One of EPCWID s largest constituents is the City of El Paso, which uses about 50,000 acre-feet of surface water in a full supply year for municipal and industrial water supply to supplement its groundwater sources. Farmers do use some 7

9 groundwater, though in general the groundwater is of lower quality than that in EBID, and may be harmful to sensitive crops. Groundwater is primarily used for irrigation when drought reduces the available surface water supply to EPCWID. HCCRD contains 18,250 water-righted acres south of El Paso County, Texas. Primary crops are cotton and alfalfa. The district is quite different from EBID and EPCWID in that it is not a part of the Rio Grande Project. The water available to HCCRD is essentially whatever flows leave EPCWID as drainage and operational spills, and so its water supply is highly unreliable and subject to severe reduction in drought. HCCRD gets maximum use out of its water supply by storing it in three relatively small reservoirs within the district, so the delivery can be managed to meet crop demands. HCCRD has one non-agricultural user, the Esperanza Fresh Water Supply Corporation, which provides water for industrial use. A summary of key characteristics of the three districts within the study area is presented below in Table 1. In considering water use for river restoration, one must first consider that the Rio Grande in the study area is fully and explicitly appropriated to the U.S. districts and Mexico. Identifying restoration activities that do not increase depletions or decrease the ability of existing water users to put water to beneficial use is a distinct possibility, and one that has been successfully used in the Project. Further implementation of such activities can be accomplished through negotiations directly with the irrigation districts, and possibly Reclamation. State agencies may also require some involvement. An example of this approach is the development of a bosque on the Picacho Drain in EBID, an ongoing project. HCCRD, in the normal operations of its regulating reservoirs, creates significant avian habitat. Obtaining water rights, through lease, purchase, or donation, and putting the water to use in restoration activities. Again, this should be discussed early and often with the irrigation districts, as any use of water for restoration would have to be coordinated with district operations, policies, and limitations. Ultimately, Reclamation and state agencies may need to be included. Water conservation measures may make additional water available for restoration. This is an attractive alternative since it promotes collaboration between river restoration and agriculture. Currently, any water savings realized by conservation is still allocated to the districts, so this approach would require negotiation with individual farmers and the districts. The first step in putting conserved water to use for river restoration would be to create, through negotiation with the districts and appropriate government agencies, the details of how the accounting and administration for conserved water would be carried out. 8

10 Elephant Butte Irrigation District (EBID) District El Paso County Water Improvement District No. 1 (EPCWID) Hudspeth County Conservation and Reclamation District No. 1 (HCCRD) Parameter Total acreage in district 133, ,000 20,176 Water-righted acreage 90,640 69,010 18,250 Actually irrigated acreage 76,000 53,000 18,250 Full supply diversion allocation, AF 495, ,862 N/A 2002 diversion charge, AF 431, , ,226* Length of canals and laterals, mi Length of lined canals and laterals, mi < ~ 0 Length of drains, mi Regulating reservoir capacity, AF 0 0 3,600 Conveyance Efficiency 65% 75% 80% Farm Application Efficiency 50-82% 50-75% ~ 50% Primary Crops Pecans Alfalfa Cotton Vegetables Cotton Alfalfa Pecans Vegetables Cotton Alfalfa Status of Adjudication Preliminary hydrographic survey complete; offers being made. Pending Pending * 2001 Table 1: Summary of characteristics of EBID, EPCWID, and HCCRD. Opportunities for conservation are evaluated in this report, and focus on the system level (river, canal/lateral systems, and return flow systems) conservation and on-farm conservation. Conventional ideas of water conservation cannot always be applied to a given system. There may be negative consequences along with the good to water conservation measures. On-farm conservation measures that increase application efficiency reduce the required application of irrigation water to achieve a given level of yield (and depletion). While this is generally a benefit, it will also reduce the return flow to drains, which provide important existing habitat. While the return flows may be reduced, their salinity and the salinity in the shallow groundwater will likely become more concentrated. It is, therefore, important to examine direct and indirect consequences of conservation measures to ensure that they are consistent with broader conservation objectives. Several potential water conservation measures are considered in the report. A summary of these methods, and their applicability to each district, is presented below in Table 1. 9

11 District Conservation Method EBID EPCWID HCCRD Canal Lining/Piping Moderate High High Rate Structures, charges to Low Low Low Constituents Release management Moderate Moderate N/A Farm Delivery Metering High Low (widely adopted) Moderate Laser Leveling Low (widely adopted) Low (widely adopted) Low (widely adopted) Pressurized Irrigation (Drip and Low Moderate Moderate Sprinkler) High Flow Turnouts Moderate Moderate Moderate Low Water Use Crops High High High Deficit Irrigation High with cotton, alfalfa; low with others High with cotton, alfalfa; low with others High Cultural Practices Moderate Moderate Moderate Table 2: Summary of water conservation potential for river restoration in the Rio Grande Project area. The ratings presented in the table are based largely on the presence or absence of downstream flow obligations (as in the case of canal lining for EBID), extent of current use of technology (laser leveling is already very widely adopted) and the nature of supply (drip and sprinkler irrigation). Low water use crops should be investigated for water use, equipment and management requirements, and market availability and reliability, but they represent potential water savings in all districts. Regardless of the means by which water for restoration is obtained, the use of existing policies, or modification of policies to facilitate restoration use, should be negotiated with the districts first. They are the most profoundly affected, and stand to regard efforts that bypass or delay their influence as an attack on their property rights. On the other hand, if consensus can be reached with one or more districts, the federal and state agencies involved tend to be amenable, as long as the plan has the districts backing. 10

12 Chapter I : Introduction This report was commissioned by the World Wildlife Fund (WWF) to explore the potential for working with agricultural water users to direct some part of the water supply of the Rio Grande in the Chihuahuan Desert to restoration of the river. While there is a long and growing history of disputes among competing water users in the Rio Grande Basin, and agricultural and environmental groups have in particular butted heads, the two groups share many common interests in future management of the river. Agricultural water use in this reach of the Rio Grande accounts for more than 80 percent of the diversions, and because irrigation was an early use, the water rights of farmers tend to be quite senior. These water rights represent a property right and a valuable asset to farmers. The goal here is to identify ways in which environmental groups can accomplish river restoration projects while respecting the established rights of irrigators by either working within the existing system or collaborating with farmers to modify the system to mutual benefit. A. Objectives The broad objectives in the production of this report are to: 1. Estimate and discuss the efficiencies of each of the irrigation districts within the study area; 2. Identify and characterize existing water conservation measures in practice within each of the irrigation districts in the study area; 3. Identify water that is currently available, or that could be made available through conservation or transfer, for riparian restoration; 4. Identify limitations and opportunities for land available for riparian restoration; 5. Identify existing or potential institutional mechanisms for managing water for riparian restoration and instream flows; 6. Create a constructive dialogue among agricultural water users and environmental interests and suggest projects aimed at obtaining and using water for restoration activities. B. Scope and Limitations The original geographic scope of this study included the southern end of the Middle Rio Grande Conservancy District (MRGCD), which also falls within the Chihuahuan Desert. However, that is a system separated by major hydrologic discontinuities in Elephant Butte and Caballo Reservoirs 11

13 from the Rio Grande Project area, and major institutional discontinuities in the Rio Grande Compact delivery point from New Mexico to Texas at Elephant Butte Dam. Other studies are currently addressing the very complicated environmental issues in the Middle Rio Grande as a whole, so the southern section of MRGCD was dropped from the scope of this study. The reach of the Rio Grande examined in this study is the Rio Grande Project area, stretching from San Marcial, New Mexico to Fort Quitman Texas. Some consideration is also given to the Forgotten Reach south of Fort Quitman to Candelaria, Texas. The study region contains three irrigation districts that are extremely different in character from each other: Elephant Butte Irrigation District (EBID) in New Mexico, and El Paso County Water Improvement District No. 1 (EPCWID) and Hudspeth County Conservation and Reclamation District No. 1 in Texas. Water is also delivered to the Republic of Mexico at the heading of the Acequia Madre into Ciudad Juàrez in this reach. A few farmers in this area do irrigate with groundwater in the area, but the virtually all of the surface water supply of the Rio Grande goes to constituents of the three districts. The three districts are the focus of this study. This study does not examine specific river restoration activities in detail. Rather, this can be considered a precursor to detailed restoration planning, as one must know what resources, and water is first and foremost, are available, and in what quantity and quality. The rules and administrative procedures that have evolved over the past century or so must also be examined, as any new use of water will have to conform to the rules, or the rules will have to conform to the new use of water. 12

14 Chapter II : The Rio Grande and its Institutions The hydrological and institutional frameworks of the Rio Grande are inexorably linked. The structure of the institutions that govern the Rio Grande evolved based on the geology and hydrology of the river, with political boundaries often being placed based on the river itself. The discussion of the Rio Grande Compact and Rio Grande Project is therefore preceded with a description of the earlier development and morphology of the river. A. Physiographic Description of Study Area The Rio Grande from San Marcial to Fort Quitman flows south across a string of basins that step downward to the south with mountain ranges on the east and west. Physiographically, the region is a part of the arid Mexican Highland Section of the Basin and Range Province (Fenneman, 1931). Geologically, the basins represent asymmetric and tilted and down-dropped fault blocks of the Rio Grande rift tectonic province (Hawley, 1978; Seager and Morgan, 1979; and Keller and Cather, 1994). The down-dropped fault blocks, called half grabens, are formed by master normal faults that displace the deepest part of the basins against uplifted and structurally-high bedrock in the region to form a complementary mountain range. The half grabens or basins are filled with up to several thousand feet of consolidated and unconsolidated alluvial fill sediments of gravel, sand, silt, and clay (Mack and others, 1998). The Rio Grande tends to traverse the basin surface closest to the master fault of the half graben (Leeder and others, 1996). The main tributaries tend to flow laterally to the Rio Grande from the side of the basin opposite the master half-graben normal fault. The Palomas-Rincon basin from San Marcial to Rincon is a good example of this configuration. The Rio Grande flows southward parallel and closest to the Fray Cristobal and Caballo Mountains. The only major basin drainages to the Rio Grande such as Percha Creek, Palomas Creek, Cuchillo-Monticello Canyon, and Nogales Canyon, flow eastward out of the distant Black Range and San Mateo Mountains far to the west on the Palomas-Rincon half graben hinge opposite the master Fray Cristobal-Caballo master normal faults to the east. Only minor drainages enter the Rio Grande from the east across the master graben faults from the Fray Cristobal and Caballo Mountains. Each basin or half graben ends when the master fault dies out and transforms into another master fault facing in the opposite or same direction (Morley, 1999). As a result, at the southern end of each basin, the Rio Grande crosses a structurally-high bedrock constriction. The narrows at 13

15 Truth or Consequences to Elephant Butte, Selden Canyon between Rincon and Radium Springs (Leasburg), and the El Paso Narrows are examples of the Rio Grande flowing from one basin to the next across a "pass" or a structural-high bedrock zones between the half grabens. These passes create separate groundwater systems such as the Mesilla Bolson aquifer system north of the El Paso Narrows and the Hueco Bolson aquifer system south of the Narrows that are linked by a common river. The development of the Rio Grande in its present course in the stretch from San Marcial to Fort Quitman was controlled by tectonism or faulting along the master half-graben faults, sediment infilling of the basin, and long-term climate changes. With sediment infilling, spill over drainage was established across the southerly bedrock constrictions of each basin and resulted in progressive integration of the main drainage (the Rio Grande) from one basin to the next (Mack and others, 1997). Prior to integration, and full sediment infilling, the basins were closed and internally drained with playa lakes or lakes in the deepest part of the basin and upstream from the southerly basin constrictions (Mack and others, 1998). Continued tectonism or down faulting of the half graben resulted in the Rio Grande migrating towards or staying close the master fault side of the basin (Leeder and others, 1996). Completion of integrated drainage to the Gulf of Mexico and major climate changes have resulted in the Rio Grande entrenching earlier basin fill to form the present day flood plain and Rio Grande Valley as base level adjusted and climate controlled river flow changes occurred (Hawley and Kottlowski, 1969). During dry (warm) times the river valley tends to back fill with flood plain sediment. During wet (cool) times the river entrenched as flow was sufficient to remove earlier basin fill along the river course. This episodic flow behavior has left a series of paired terraces above the flood plain of the Rio Grande Valley and below the basin floor surfaces that formed prior to Pleistocene entrenchment of the river system. During the 19 th and 20 th centuries, engineered modifications to the area have included the construction of simple irrigation works in the 1800s and the much more comprehensive Rio Grande Project in the 1900s. The Rio Grande Project and its additions have included storage and diversion dams, canalization of much of the river, flood control dams on tributary arroyos, canal and drainage systems, and clearing and leveling of agricultural lands. These alterations are discussed in more detail in the descriptions of the Rio Grande Project and the individual districts. 14

16 B. The Rio Grande Compact The law of the river in the Chihuahuan Desert portion of the Rio Grande is the Rio Grande Compact adopted December 19, 1939 among Colorado, New Mexico, and Texas. The stated purpose of the compact is to remove all causes of present and future controversy among these States and between the citizens of one of these States and citizens of another State with respect to the use of the waters of the Rio Grande above Fort Quitman, Texas The region covered by the Compact is shown in Figure 1. While much of the Compact area is outside of the Chihuahuan Desert, an understanding of its workings is absolutely necessary to understand the management of water and attitudes of the players in the study area. The Rio Grande Compact is administered by a commission with representations from each of the three Compact states, Colorado, New Mexico, and Texas. A fourth non-voting member is appointed by the President of the United States. The Colorado and New Mexico commissioners are the State Engineers of the respective states. The Texas commissioner is appointed by the Texas governor. 15

17 Figure 1: Rio Grande Compact area. From Report of the Rio Grande Compact Commission, The Compact uses measured flows at index gages on the Rio Grande and its tributaries to quantify delivery obligations from Colorado to New Mexico and from New Mexico to Texas. Because the Rio Grande Project, consisting of EBID in New Mexico and EPCWID in Texas, was operated as a single irrigation system at the time of the signing of the Compact, and because the project straddles the New Mexico-Texas state line, the Compact specified deliveries to Texas at San Marcial gage, above Elephant Butte Reservoir. For operational reasons, the delivery point to Texas was moved to Elephant Butte Reservoir in The various index gages that determine the 16

18 state-to-state delivery obligations are shown in Figure 2. This arrangement places EBID in the Texas portion of the Compact, represented by a political appointee from Texas. The resulting feeling of disenfranchisement is strong with EBID farmers. Figure 2: Rio Grande Compact index gages. From Report of the Rio Grande Compact Commission,

19 Beginning in Colorado, the Compact specifies the delivery obligation of Colorado to New Mexico in terms of the flows in the Conejos River system and in the main stem of the Rio Grande. The Compact specifies a required flow in the Conejos near Mouths, Colorado, measured at the USGS gaging station near Los Sauces, Colorado, (Station 6 in Figure 2) above the confluence with the Rio Grande based on the Conejos Index Supply. The Conejos Index Supply is the sum of measured flows at the following USGS gaging stations: 1. Conejos River near Mogote, Colorado during the calendar year (Station 3 in Figure 2); 2. San Antonio River at Ortiz, Colorado, April to October, inclusive (Station 4 in Figure 2); 3. Los Pinos River near Ortiz, April to October, inclusive (Station 5 in Figure 2). The relationship between the Conejos Index Supply and the flow obligation in the Conejos at Mouths is show below in Table 3. Conejos Index Supply 1,000 AF Conejos River at Mouths 1,000 AF Conejos River at Mouths, 1000 AF Conejos Index Supply, 1000 AF Table 3: Conejos River at Mouths (Los Sauces) as a function of Conejos Index Supply. Column numbers (1) and (2) refer to the column designations in the Rio Grande Compact. The Conejos River at Mouths and the Rio Grande measured at the USGS gaging station near Del Norte, Colorado define a flow obligation at the USGS gaging station at Lobatos, 18

20 Colorado, near the New Mexico state line (Station 7 in Figure 2). The Del Norte flow is adjusted to account for the hydrologic effects of post-1937 upstream reservoirs. Lobatos is Colorado s delivery point to New Mexico. Colorado s obligation is ten thousand AF less than the sum of the indicated flows for Conejos at Mouths from Table 3 plus the Rio Grande at Lobatos less Conejos at Mouths from Table 4: Rio Rio Lobatos Del Norte less 1,000 AF Mouths 1,000 AF Rio Lobatos less Mouths, 1000 AF Rio Del Norte, 1000 AF Table 4: Rio Grande at Lobatos as a function of Rio Grande at Del Norte. The basic idea behind the delivery requirement from state to state is evident in these graphs. At low levels of flow, the upstream state (Colorado, in the above two tables) gets a higher percentage of the available supply, but as the supply increases, the downstream state s (New Mexico in above tables) gets an increasing percentage, until each acre-foot of additional flow at the index point results in an acre-foot of required delivery at the state line. The Compact specifies that New Mexico s obligation to deliver water to Texas is based on flow measured at the USGS gauging station at Otowi Bridge, New Mexico, below the confluence of the Rio Grande and Rio Chama (Station 14 in Figure 2). In the original Compact, deliveries to 19

21 New Mexico were made at the San Marcial gauging station upstream of Elephant Butte Reservoir, and deliveries excluded flows during the months of June, July, and August. In 1948, this was amended by resolution to provide accounting for deliveries to New Mexico on a year-round basis at Elephant Butte Reservoir. As defined in the 1948 resolution, the Otowi Index Supply is the actual flow measured at Otowi Bridge corrected for operations of any reservoirs constructed since 1929 between Lobatos and Otowi, and corrected for transbasin diversions. The Otowi Index Supply actually determines New Mexico s annual delivery obligation to Texas. This obligation is the Elephant Butte Effective Index Supply, which is compared to the actual algebraic sum of the annual releases from Elephant Butte Reservoir plus any change in Project Storage, with increases being positive and decreases being negative. Rio Grande Project Storage, commonly referred to as Project Storage, is the sum of the water stored in Elephant Butte and Caballo Reservoirs. This arrangement places the burden of losses in Elephant Butte Reservoir due to evaporation and seepage on New Mexico, because the hydrologic balance yielding New Mexico s delivery to Texas release plus change in storage implicitly subtracts reservoir losses from New Mexico s delivery. Credits, discussed later, are subject to evaporation adjustments. However, the objective in establishing the Otowi-Elephant Butte Index relationship was to make it equivalent to the original deliveries scheduled for San Marcial. The relationship between the Otowi Index Supply and New Mexico s obligation to deliver water to Elephant Butte Reservoir is shown below in Table 5: 20

22 Otowi Index Supply 1000 af Elephant Butte Index Supply 1000 af Elephant Butte Index Supply, 1000 AF Table 5: Elephant Butte index as a function of flow at Otowi Bridge. Otowi Index Supply, 1000 AF In practice, it is virtually impossible for one state to exactly meet its delivery obligation to its downstream neighbor, so a system of debits and credits was developed in the Rio Grande Compact. An annual credit or debit to Colorado is calculated as the difference between the actual adjusted flow at Lobatos minus Colorado s obligation to deliver water at Lobatos. An annual credit occurs when the algebraic sign is positive, and a debit occurs when the algebraic sign is negative. An annual credit or debit to New Mexico is calculated as the difference between the adjusted sum of releases from Elephant Butte Dam and changes in Project Storage (the Elephant Butte Effective 21

23 Index Supply) and the Elephant Butte Index as determined from Table 5 based on the Otowi Index Supply. An annual credit to New Mexico occurs if the algebraic sign is positive, and an annual debit occurs if it is negative. Annual Debits are the amount of water that, in a calendar year, Colorado may fall behind in its deliveries to New Mexico or New Mexico may fall behind in its deliveries to Texas. Credits are similar over-deliveries. Accrued debits and credits are the running sum of annual debits and credits between states. Colorado may not exceed 100,000 acre-feet for either an annual or accrued debit, unless the debit in excess of this amount is caused by Colorado s holding water over in storage in reservoirs constructed after 1937 (including Squaw Lake, Rio Hondo, Hermit Lakes, Troutvale No. 2, Jumper Creek, Big Meadows, Alberta Park, Mill Creek, Fuchs, and Platoro reservoirs, as well as the enlarged portion of the Shaw Lake enlargement) in the basin above Lobatos. Colorado is required to retain water in storage in such reservoirs to the extent of its accrued debit. New Mexico s accrued debit may not exceed 200,000 acre-feet, unless the debit in excess of this amount is caused by holdover water in post-1929 reservoirs between Lobatos and San Marcial (Heron, El Vado, Abiquiu, Nambe Falls, McClure (Granite Point), Nichols, Cochiti, and Jemez Canyon reservoirs). New Mexico is required to retain water in storage in such reservoirs to the extent of its accrued debit. New Mexico s annual debit may not exceed the sum of 150,000 acrefeet and all gains in the quantity of water in storage during the year. Both Colorado and New Mexico are limited to a maximum annual credit of 150,000 acrefeet. Presumably, water delivered in excess of 150,000 acre-feet over the index requirement would be free water to the downstream state. Credit water for Colorado and New Mexico is stored in Elephant Butte and Caballo Reservoirs, and diminished by evaporation. This credit water is not available for release as usable water to Texas water users, except when credits are relinquished to allow the upstream states to store water in post-compact reservoirs during times of low Project Storage under Article VII, as further discussed below. The Texas portion of the Compact, the Rio Grande Project, has no downstream delivery obligation other than to Mexico. The usable water in Project Storage is the total Project Storage less credits for New Mexico and Texas and the generally minor amounts of San Juan-Chama Project imported water stored there. Complicating the accounting for delivery debits and credits is the concept of the spill. An actual spill occurs when Project Storage in Elephant Butte and Caballo Reservoirs reaches its 22

24 capacity, and water either flows over the spillway crest at Elephant Butte Dam or releases are made to maintain flood storage capacity in Elephant Butte Reservoir in excess of downstream demands. A hypothetical spill occurs when reservoir water would have actually spilled, had an annual release of 790,000 acre-feet been made every year since the previous spill. All credit water in storage must have been spilled before either an actual or hypothetical spill can occur. Spills are of particular importance because in the event of a spill, all accrued debits of Colorado and New Mexico are cancelled. Accrued credits for the two states are reduced in an amount equal to the quantity spilled, reducing each state s accrued credits proportionally to each state s respective credit balance. As noted previously, Colorado must maintain water in storage above Lobatos in an amount equal to any debit balance that Colorado may accrue, and New Mexico must hold water in storage between Lobatos and San Marcial equal to any debit balance that it accrues. If a state has an accrued debit balance, the downstream state or states may, at the beginning of the year, call for the release of the upstream stored water. The downstream states may call for the repayment of accrued debits sufficient to bring the usable water in Project Storage to 600,000 acre-feet by March, and enough to make a normal release of 790,000 acre-feet during the year. Clearly, an accrued debit balance is an unattractive position for Colorado or New Mexico to find themselves in, and both have maintained accrued credit balances in recent years. The fact that a state must have an amount of water equal to its accrued debit balance in case the downstream state or states call for it gives little advantage to running an accrued debit on downstream deliveries. Accrued credits, however, allow an upstream state to deliver less than the index amount, with the downstream state relying on the equivalent amount of water in Project Storage. Article VII addresses management and accounting when Project Storage is very low. If the amount of usable water in Project Storage drops below 400,000 acre-feet, neither Colorado nor New Mexico may increase the amount of water in storage in post-1929 upstream reservoirs. This applies when the releases since the last spill do not average more than 790,000 acre-feet per year. If the previous releases do average more than 790,000 acre-feet per year, accounting adjustments are made to compensate for the excess release. Article VII also provides for Colorado and New Mexico to allow the release of credit water they may have in Project Storage, and storing a like amount in their upstream post-1929 reservoirs. It is interesting to note that in June 2002, Article VII was invoked due to low storage levels. 23

25 The Compact specifically states in Article XI that all controversies between said States relative to the quantity or quality of the water of the Rio Grande are composed and settled; however, nothing herein shall be interpreted to prevent recourse by a signatory state to the Supreme Court of the United States to redress should the character or quality of the water, at the point of delivery, be changed hereafter by one signatory state to the injury of another. Nothing herein shall be construed as an admission by any signatory state that the use of water for irrigation causes increase of salinity for which the user is responsible in law. An example of Compact accounting may help to illustrate how the Compact works. Table 6 through Table 8 are taken from the Report of the Rio Grande Compact Commission, Beginning with Colorado in Table 6, Colorado began the year with a 17.7 kaf (thousand acre-feet) accrued credit in its deliveries to New Mexico (column 23, row C1). The total flow from the Conejos at Mogote, Los Pinos near Ortiz, and San Antonio at Ortiz is kaf (Column 5, sum). This is adjusted for changes in storage and post-compact reservoir evaporation (columns 7 and 8, respectively) to arrive at the Conejos Index Supply of kaf (column 10, sum). Entering Table 3 with this quantity gives a required flow from the Conejos at Mouths of 17 kaf (column 21, C2). The Rio Grande at Del Norte gage shows an annual total measured flow of kaf (column 12, sum). This is corrected for changes in storage, reservoir evaporation, and transmountain diversions for an adjusted Del Norte index of kaf (column 18, sum), resulting in a value of Lobatos less Conejos at Mouths of 95.8 kaf (column 21, C3) from Table 4. The scheduled delivery at Lobatos is then the Conejos flow plus the Rio Grande flow minus 10 kaf, or kaf. The actual flow at Lobatos was kaf (column 22, sum), resulting in a credit of 11.4 kaf. This credit is reduced by 2.1 kaf for evaporation, producing a net annual credit for Colorado of 9.3 kaf which, when added to the beginning accrued credit of 17.7 kaf, yields a yearend accrued credit of 27.0 kaf (column 23, row C8). 24

26 RIO GRANDE COMPACT - DELIVERIES BY COLORADO AT STATE LINE YEAR 2000 Quantities in thouseands of acre feet to nearest hundred Month CONEJOS AT MOGOTE CONEJOS INDEX SUPPLY MEASURED FLOW ADJUSTMENTS SUPPLY LOS PINOS NEAR ORTIZ SAN ANTONIO AT ORTIZ TOTAL STORAGE AT END OF MONTH CHANGE IN STORAGE OTHER ADJUSTMENTS a NET ADJUSTMENTS SUPPLY IN MONTH ACCUMULATED TOTAL RECORDED FLOW NEAR DEL NORTE STORAGE AT END OF MONTH RIO GRANDE INDEX SUPPLY ADJUSTMENTS CHANGE IN STORAGE TRANSMOUNTAIN DIVERSIONS b OTHER ADJUSTMENTS a NET ADJUSTMENTS SUPPLY IN MONTH SUPPLY ACCUMULATED TOTAL CONEJOS RIVER AT MOUTHS NEAR LOS SAUCES DELIVERIES RIO GRANDE LESS CONEJOS RIVER RIO GRANDE AT LOBATOS ACCUMULATED TOTAL AT LOBATOS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR Remarks: Col. 6 does not include transmountain water. SUMMARY OF DEBITS AND CREDITS a Evaporation loss post compact reservoirs; report of the Engineer Adviser for Colorado. ITEM DEBIT CREDIT BALANCE b 884 ac-ft minus 243 ac-ft pre-compact; report of the Engineer Adviser for Colorado. C1 Balance at Beginning of Year 17.7 C2 Scheduled Delivery from Conejos River C3 Scheduled Delivery from Rio Grande C4 Actual Delivery at Lobatos plus 10,000 Acre Feet C5 Reduction of Debits o/c Evaporation C6 Reduction of Credits o/c Evaporation and Spill C7 C8 Balance at End of Year 27.0 Table 6: Colorado deliveries to New Mexico, The calculation for the delivery of water by New Mexico to Texas at Elephant Butter Reservoir is presented below in Table 7. In that table, New Mexico starts the year with a credit balance of kaf. The recorded flow at Otowi was kaf. Net adjustments are the algebraic sum of the change in reservoirs between Lobatos and Otowi that would affect the Otowi flow (-73.3 kaf), reservoir evaporation from those reservoirs (2.5 kaf), the transmountain diversions from the San Juan-Chama Diversion Project ( kaf), for a total net adjustment of kaf. This produces an Otowi Index Supply of = kaf. Entering Table 5 with an Otowi Index Supply of kaf, the resulting Elephant Butte Index Supply of kaf, shown in NM2 column 14 of Table 7. The actual delivery, or effective supply to Elephant Butte, equal to the release from Elephant Butte plus the change in Project Storage, was kaf, shown in NM3, column 15. New Mexico s credit was reduced by 20.2 kaf for reservoir evaporation (NM5, column 14), so the net change in New Mexico s credit is the effective supply (353.6 kaf) less the Elephant Butte Index Supply (233.3 kaf) less reservoir evaporation (20.2 kaf) for a net change of kaf. New Mexico s ending balance is the beginning balance of kaf plus the net change of kaf, for year-end credit of kaf (NM8, column 16). 25

27 MONTH OTOWI INDEX SUPPLY ADJUSTMENTS RESERVOIRS: LOBATOS TO OTOWI Other Adjustments Recorded Flow at Storage End Otowi Bridge Change in of Month a Storage Reservoir Evaporation RIO GRANDE COMPACT - DELIVERIES BY NEW MEXICO AT ELEPHANT BUTTE YEAR 2000 Quantities in thousands of acre feet to nearest hundred Transmouintain Diversions Net Adjustments INDEX SUPPLY During Month Accumulated Total Total Water Stored in New Mexico Above San Marcial at End of Month a STORAGE IN ELEPHANT BUTTE RESERVOIR ,706.1 JAN , FEB , MAR , APR , MAY , JUN , JUL , AUG , SEP , OCT , NOV , DEC , YEAR Remarks: Cols. 3, 11, and 12 do not include transmountain water. SUMMARY OF DEBITS AND CREDITS ITEM DEBIT CREDIT BALANCE Cols. 3 and 11 reflect implementation of revised area-capacity tables for Abiquiu, Cochiti, NM1 Balance at Beginning of year and Jemez Canyon Reservoirs, effective January 1, NM2 Scheduled Delivery at Elephant Butte NM3 Actual Elephant Butte Effective Supply NM4 Reduction of Debits o/c Evaporation NM5 Reduction of Credits o/c Evaporation and Spill NM6 NM7 NM8 Balance at End of Year End of Month a ELEPHANT BUTTE EFFECTIVE SUPPLY Effective Supply Recorded Flow Below Elephant Butte Dam Change Gain(+) Loss(-) During Month Accumulated Total Table 7: New Mexico Deliveries to Texas. Finally, the calculations for Project Storage and Release are presented in Table 8. The total Project storage capacity at the end of the month is the total capacity of Elephant Butte Reservoir less the required flood control space, which is 50 kaf from April through September, and 25 kaf from October through March. The total usable water in storage is the actual amount in Elephant Butte and Caballo Reservoirs less New Mexico and Colorado s credit water. The credit water for New Mexico and Colorado start at the previous year end value (also listed in Table 6 and Table 7) and is reduced each month for evaporation. The total project water in storage is the sum of the usable water in storage and the credit water for Colorado and New Mexico. Intervening diversions to canals refers to the small lateral diverting water directly from Caballo Dam, the Bonito Lateral. The measured flow below Caballo plus the Bonito Lateral gives the total release and spill for the year. In 2000, there was no spill, so all of the release was usable release, which totaled kaf. At the end of 1999, the release was cumulatively 38.3 kaf short of normal (P1, column 19). The release for 2000 was 37.6 kaf short of normal, so the accrued deviation from normal release is 75.9 kaf (P7, column 19) at the end of