Summary of Ecosystem Services of Riparian Restoration: A Review of Rock Detention Structures in the Madrean Archipelago Ecoregion
Feb. 26, 2021
The WRRC is pleased to feature the following article summary prepared by the author, US Geological Survey research scientist (and UArizona Affiliate), Dr. Laura M. Norman.
The US Geological Survey (USGS) Aridlands Water Harvesting Study has been investigating the potential to sculpt landscapes in the Madrean Archipelago Ecoregion and quantifying impacts (on hydrology, vegetation, and sediment) over the past 10 years. This article first introduces the long history of rock detention structures (RDS) locally, as agricultural tools, and then summarizes results of a multi-year research project conducted on RDS being used for restoration. The study area is the Madrean Archipelago Ecoregion, along the US-Mexico border, a biodiversity hotspot of the planet. Ecosystem services of RDS are described with examples from analyses. I argue that global water availability may be one facet of the environment not yet being properly accounted for economically and propose using tradeoffs among ecosystem services to safeguard ephemeral riparian areas (i.e. to offset footprints of groundwater pumping downstream through the investment of RDS installations or to compensate practitioners if RDS can be used to offset greenhouse gas emissions).
Major ecosystem services described by the USGS Aridland Water Harvesting Study are vetted with associated research (with citations available in the article):
- Flood regulation: in the cross-border urban environment of Nogales, Arizona, US, and Nogales, Sonora, Mexico, models assessed flood vulnerability and portrayed impacts RDS would have in reducing peak flows, prioritizing some locations as being more beneficial than others.
- Habitat provisioning: multiple studies address the potential for RDS to maintain and improve riparian vegetation and water availability. A remote-sensing analysis was conducted to document impacts of RDS installed at Cienega San Bernardino, over 20+ years, to restore surface water for native fishes. Results portray live green vegetation present at most sites treated by gabion installation vs. control sites and the potential of RDS to increase vegetation as far as 5 km downstream and 1 km upstream. A field study was launched in 2014 to monitor locations with on-the-ground measurements, with preliminary findings portraying increases of perennial vegetation at RDS.
- Water regulation, purification, and provisioning: a paired-watershed approach was established at El Coronado Ranch to analyze the impacts of RDS on hydrologic function. Results portray a reduced peak flow response but increase of 28% more flow volume per area in the treated watershed. At the Babocomari Ranch, field experiments were coupled with surface and groundwater modeling to investigate using RDS to augment aquifer recharge with average infiltration behind the RDS increasing ~10%. Model results indicated a potential increase in lateral soil water incurred from RDS installation.
- Erosion regulation: at the Deep Dirt Farm Institute, runoff, sediment transport, and geomorphic modeling with repeat terrestrial laser scanner (TLS) surveys were used to map landscape change at RDS. Findings support erosion control and the potential to use models to predict hydraulics and approximate associated trends and patterns of aggradation and degradation resulting from gabions before they are installed.
- Carbon sequestration and storage: a pilot study evaluated stable isotope ratios of carbon and nitrogen at and around RDS at El Coronado Ranch. Results indicate the potential of check dams to increase carbon sequestration, especially in burned watersheds.
- Social value: a study was developed to identify spatial guidelines for restoration efforts. Borderlands Restoration Network initiated a social survey to solicit perceived, nonmarket values related to restoration and conservation. A model was applied to map survey responses across the watershed that documented values focused on streams and the life-sustaining services, biological diversity, and aesthetics.
In addition to the ecosystem services described, the various techniques for monitoring the success of structures are offered as possible tools or methodologies useful for further investigation.
Figure: Location map portraying Aridland Water Harvesting Study locations in relationship to hydrography, state and federal boundaries, and watersheds in the United States-Mexico borderlands study area.
Figure: Photos of large structures: (A) Looking downstream at Cinco de Febrero, which experiences major flooding during monsoons, in Nogales, Sonora, Mexico (photo by Hans Huth [April 12, 2010]); (B) Gabion in Hay Hollow at Rancho San Bernardino, Sonora, Mexico (photo by Josiah Austin [October 27, 2001]); (C) Gabion in Vaughn Canyon on the Babacomari Ranch (photo by James Callegary June 19, 2015); and (D) Gabion installed at Bone Creek on the Deep Dirt Farm Institute (photo by Kate Tirion (2014).
Figure: Photos of small structures at (A) Turkey Pen in the El Coronado Ranch (photo by Leila Gass, March 23, 2016); (B) Bar Boot Allotment on the Douglas Ranger District, USFS (photo by Natalie R. Wilson, July 19, 2019); (C) Tex Canyon on the Douglas Ranger District, USFS (photo by Natalie R. Wilson, July 14, 2015); (D) Silver Creek on the Malpai Ranch (photo by Natalie R. Wilson, September 12, 2016).