Going to the MAT for Water Management along the Middle Rio Grande

Concern is building on how the multiple years of annually low mountain snowpack and extended durations of drought are combining to cause decreasing water supply to the Rio Grande and other NM rivers. Accompanying these concerns is the recognition that improved approaches and methods to achieve effective and innovative water management practices are needed to better address these changing conditions for the Rio Grande and across NM.

The following presents an example useful in helping to build the needed approaches. It comes from a little-known ad hoc group formed in 2012 that has been successful in developing a high degree of cooperation, nearly a comradery, among resource managers and scientists leading annually to recommended water operations to water management agencies for the Middle Rio Grande. This group is named the Minnow Action Team, which is commonly called the “MAT.”

The MAT was initially envisioned by NM Interstate Stream Commission (ISC) staff to be implemented as part of a recovery effort for the Rio Grande Silvery Minnow (RGSM). Populations of this fish once extended from about Velarde to near the Gulf of Mexico, but its current range is limited to the MRG. As such, it is now listed as endangered under the federal Endangered Species Act (ESA). When formed, the purpose of the MAT was to serve as a communication link between annual MRG water operations and RGSM recovery efforts. The need for a group such as the MAT became apparent during the drought year of 2012 and has continued to be a great forum to address challenges collaboratively for these two groups of managers building from the input of the region’s scientists.

Here it is important to recognize that the MAT has as its overarching goal to aid in the persistence and recovery of the endangered RGSM, with secondary goals related to other ESA listed species along the MRG. In contrast, overall water management for the MRG and other river systems includes needs to address multiple issues and goals, which may include, for example, not only listed species but also compact compliance, agricultural, municipal, industrial, recreational, conservation, and other needs. With multiple goals, the analysis and management decisions become more involved, difficult and impactful. Thus, when considering the MAT and its operations, we need also to think about how the MAT’s example can be best extended to address multiple goals for managing the river’s annually changing available water supply.

The MAT now meets each year in early February and then again in both March and April, before and during the initiation of the runoff and irrigation seasons. These meetings generally include technical staff from the ISC, U.S Bureau of Reclamation (USBR), Middle Rio Grande Conservancy District (MRGCD), US Army Corps of Engineers (Corps), US Fish and Wildlife Service (FWS), NM Department of Game and Fish (NMGAF), City of Albuquerque (ABQ), Albuquerque Bernalillo County Water Utility Authority (ABCWUA), local consultants, interested citizens, and others. The MAT is chaired by the ISC and MRGCD.

An early focus of each meeting is a presentation and discussion of results from USBR, Corps, and ISC modelers on projections for the coming year’s water supply, reservoir storage, river flow, and, often, how the projections may affect New Mexico’s compliance with the Rio Grande Compact. The model projections presented are based on the most current data on snowpack water volumes, current projections for upcoming temperature and weather patterns, and irrigation management plans.  

Modeling is done primarily using the Upper Rio Grande Water Operations Model (URGWOM), which was initially developed nearly two decades ago as part of an Environmental Impact Statement Assessment for Middle Rio Grande (MRG) water operations. This model has been regularly updated and refined. In use, the model matches current and projected hydrologic, management, and environmental conditions with similar historical conditions to project river flows for the water year.

The URGWOM projections and subsequent discussion are followed by additional presentations by FWS and often other biologists describing what is known about the numbers of RGSM collected in relation to their distribution along the three major reaches of the MRG (Angostura/Albuquerque, Isleta, and San Acacia reaches). The data presented come from the previous year’s fish monitoring records and any more recent information that may be available. Also presented are actions that the FWS has completed and expects to implement for its annual RGSM population augmentation (stocking) by river reach. Some meetings also include presentations updating how trends of RGSM populations have increased or decreased over the years in relation to MRG flows. These presentations may also describe observed RGSM population relationships compared to habitat restoration projects and other habitat conditions.

Here it is important to recognize there are two primary critical periods in the RGSM’s annual life cycles:

First, spring flow pulses initiate their primary annual spawns. Increases of numbers of young RGSM in the MRG have been documented to increase progressively with the increasing spring flows that, in turn, increase the extent and duration of inundation along the MRG floodplain (its “bosque”). Some consider that this relationship exists because through the history of the Rio Grande, before the MRG channel became extensively managed by channelization, levees, and jetty jacks, the spring floods would often inundate its floodplain for hundreds of yards and, in some years and in some places, up to a mile or more along one or both sides of the Rio Grande. This flooding changed some portions of the river into what could be characterized as “slow-flowing lakes.” In these new shallow-water habitats, the water tends to warm quicker and abundant newly wetted food resources for the young RGSM become readily available. Both conditions tend to enhance the growth rates and survival of the young RGSM. Later, as the flood waters recede, most RGSM still remaining on the floodplain appear inherently to know that it is time to swim to the river.

Recognizing the importance of floodplain connectivity to the MRG not only for RGSM but for native riparian vegetation, multiple entities (ISC, BR, MRGCD, ABQ, Pueblos, and others) have constructed a diversity of habitat restoration projects to reconnect the floodplain to the river during spring flows along with other hopefully beneficial habitat enhancements. Monitoring has documented the presence of reproductively-ready RGSM when floodplains begin to become inundated and also has collected high numbers of RGSM eggs from the inundated floodplain habitats. The need to understand what the hydrology will produce in a given year for overbank inundation is essential for researchers to target their investigations and also allows biologists to advise hydrologists on flow management options to potentially implement.

The second critical junction in annual lifecycle for RGSM is survival during the summer drying periods. Historically, the Rio Grande flowed near to its underlying groundwater. During periods of channel drying, which historical records indicate did occur along the Rio Grande, the deeper scoured pockets in the riverbed could connect with the underlying groundwater to produce natural refugia pools in which often large numbers of the RGSM population survived.

With channel management and valley dewatering over the past century, the river has become largely disconnected from its now much deeper underlying groundwater. As such, the natural refugia pools no longer form, with the resulting extensive mortality of RGSM and other fish in reaches where MRG channel drying occurs, particularly along the Isleta Reach. To address this change, the FWS has led annual rescue and salvage efforts collecting RGSM from drying pools to move them into parts of the MRG where flow persists. During the MAT presentations, local consultants report on their documented daily observations on where the MRG channel had dried (called “River Eyes”) and the FWS reports on the past year’s efforts and successes on rescuing and moving RGSM from drying pools.

Other discussions during the typical two-hour MAT meetings include biologists from Albuquerque’s RGSM Rearing and Breeding Facility, who lead efforts to collect spring-spawn RGSM eggs from the river channel, discuss upcoming collection plans and needs for volunteer help. Also, ISC and BR describe developing plans for continued RGSM population monitoring along the river and in floodplains, operating River Eyes, and constructing any new habitat restoration projects. FWS characterize likely RGSM rescue operations.

The February MAT meetings conclude with open discussions on the preceding presentations to start defining how the MRG flows might be best managed to balance needs for successful spring spawns and RGSM population recruitment versus needs to minimize summer channel drying and resulting mortality of young and old RGSM. Tentative plans for river operations are defined during the February meeting. These are then refined during its March meeting as snowpack-stored water data are updated. In the April meeting, after this information has been further refined and model projections again are updated, the coming year’s water recommended operation plans are finalized. These may be modified later during the daily irrigation-season phone calls for river-operations among the agencies and consultants, whenever substantive MRG flow changes may occur, such as a major storm that significantly increases water in the watershed.

One innovative water management technique originally proposed by the MRGCD and recommended by the MAT is known as “the jiggle.” This operation now may be recommended whenever low spring runoff projections cause concern about insufficient flow to produce an RGSM spawn. For example, in one year under the jiggle, as the minimal spring runoff began to flow into the MRG, the bladder dam operated by ABCWUA was raised to its maximum height, backing up as much water as possible behind it. This dam was then dropped as quickly as possible, creating a small flow pulse downstream. During the same period, MRGCD closed the gates at the Isleta diversion structure, backing up the river flow upstream. Then, as the ABCWUA released pulse reached that structure, the gates on the Isleta dam were quickly opened producing a somewhat larger flow pulse that propagates downstream.  Monitoring the three coordinated jiggles that year revealed moderate success enhancing numbers of collected RGSM eggs, particularly in the Isleta Reach.  The greatest spawn benefit occurred when one jiggle was fortunately enhanced by a passing rainstorm. It is likely that additional jiggles with monitoring will be conducted in future years, whenever low spring-flow volumes indicate similar actions to again be appropriate.

The MAT clearly demonstrates how collaborative joint management decisions based on solid technical information and respectful discussion can produce successful resource management results. It should be noted again that the MAT deals with management options primarily focused on goals for a single endangered fish species. Whenever such iterative planning and management efforts (often called “adaptive management”) are expanded to a diversity of goals, as noted above, the collaborative discussions, analyses and management decisions become more involved, difficult, and impactful. The most successful water management groups first narrow their targeted goals, at least initially, to the one or a few of those having the greatest sensitivity and potentially the most adverse consequences. Coordinated discussions among those from the individual stakeholder groups, with necessary give-and-take, can result in plans based on sound technical information and produce successfully implemented resource management results.

(Photographs used by permission: Michael Hatch-3.4 inch RGSM photo; Michael Marcus-overbank flooding and bladder dam photos.)