Drawings by Chloé Fandel, Graduate Student at the University of Arizona
Figure 1. Ecosystem Services of rock detention structures.
Figure 2. Ecosystem Services derived scientific question that our project addresses.
Figure 3. Schematic of hydrologic cycle (aka. Water budget)
Aridland Water Harvesting Study
Most of western North America has been severely grazed by cattle, causing grasslands to deteriorate and desert scrub expansion. Climate in arid and semi-arid regions is often typified by short, intense rainfall events which contribute to short-term flooding and erosion. Associated arroyo cutting occurs when ephemeral creek beds are carved into the floodplain when erratic overland flow occurs; this lowers water tables, depleting surface and subsurface water supplies (Betancourt and Turner 1993).
When surface runoff is high, little recharge infiltrates to the basin aquifer, and high-intensity flow transports heavy sediment loads to channels, contributing to nonpoint source pollution in surface water bodies. People living in arid land environments all over the globe have developed ways to manipulate the earth’s surface to benefit and sustain agricultural practices via water harvesting. Archaeologists have discovered such features dating back to 27 B.C. and in the Madrean Archipelago Ecoregion (Sky Islands) to 1000 A.D. (Fish et al. 2013).
The Madrean Sky Island Archipelago (Warshall 1995), part of the Basin and Range physiographic province, extends along the international border between the United States and Mexico, and has been identified as one of the most vulnerable areas to climate change (Seager et al. 2007). It is characterized by broad valleys or basins separated by steeply rising mountain ranges with independent hydrologic systems --classified as desert but renowned for its lush vegetation and diverse aquatic habitats, remnants from a time when the area was wetter.
Federal agencies, including the US Forest Service, US Fish and Wildlife Service, US Parks Service, and Bureau of Land Management, are major land managers in this region, concerned with developing sustainable water supplies and vegetation for future generations and engage in best management practices. Additionally, private ranch owners have identified an immediate need for the adoption of proper conservation strategies in this area to control the eutrophication in downstream water supplies and to prevent further watershed degradation.
One solution is to install rock detention structures, such as (i.) a one rock dam (one-rock high) bed of rocks (en espanol: trinchera) can be in channels or hillslopes, (ii.) a check dam (gully plug), usually ~3 foot high loose rock structure set into channel, and/or (iii.) a rock gabion, which consists of rocks rapped in wire cage and keyed into channel (see Drawings)
Broad Science Questions
As such, we have developed a series of scientific questions to address their impacts both qualitatively and quantitatively, and the list keeps growing (Fig. 2).
1. Determine metrics to discern effectiveness of rock detention structures (quantifiable results).
2. Work with partners to determine where new structures should be…..
- For flood prevention?
- For vegetation and habitat?
- To “heal” the land?
- For groundwater recharge?
- To reduce erosion and nonpoint source pollution (sedimentation in streams)?
- To increase surface water?
- To armor landscapes?
Our research is based on the hydrologic cycle that describes water as either: a) evaporated or transpired to the atmosphere; b) stored in the soil or in underground aquifers; or c) discharged to a nearby waterway (Fig. 3).
- Terrestrial monitoring documents the hydrological impacts of water harvesting devices and helps identify sites for future installation in Patagonia.
- Landsat Thematic Mapper satellite imagery and the derived Normalized Difference Vegetation Index (NDVI) values are being used to monitor changes in vegetation greenness at a desert wetland in San Bernardino.
- Hydrological geospatial models, including the Soil and Water Assessment Tool (SWAT) and the Kinematic Runoff and Erosion Model (KINEROS2) are being used (with Terrestrial LiDAR (T-LiDAR) datasets) to monitor changes in surface flow, infiltration, and sediment build-up at new check dams and detention features in Nogales, Patagonia, and at the Babocomari.
- T-LiDAR data and 2-D hydraulic models are also being used to examine changes in vegetation structure and channel dimensions in Patagonia.
- Hydrographs are developed using Continuous Slope Area methods to be input to calibrate watershed models for long-term predictions in the Chiricahua Mountains.
The U.S. Geological Survey (USGS) is a Federal agency that conducts science about the Earth, its natural and living resources, natural hazards, and the environment. This research is part of the Climate and Land Use (CLU) Change Mission Area of the USGS, which undertakes scientific research using monitoring, remote sensing address the effects of climate and land use change. The CLU provides the scientific foundation upon which policymakers, natural resource managers, and the public make informed decisions about the management of natural resources. Funding comes from the Land Change Science (LCS) Program to understand the patterns, processes, and consequences of changes using models to predict scenarios of future conditions, and conduct integrative, holistic assessments.
Point of contact: Laura M. Norman, Ph.D. (520-670-5510)
Betancourt, Julio Luis, and Raymond Turner. 1993. “Tucson’s Santa Cruz River and the Arroyo Legacy”. Ph.D., Tucson, Arizona: University of Arizona.
Fish, Suzanne K., Paul R. Fish, Russel Varineau, and Elisa Villalpando. 2013. “In Flight: Adriel Heisey’s Images of Trincheras Archaeology.” An Exhibition of Arizona State Museum and the Mexican National Institute of Anthropology and History. www.statemuseum.arizona.edu/exhibits/heisey/index.shtml.
Seager, Richard, Mingfang Ting, Isaac Held, Yochanan Kushnir, Jian Lu, Gabriel Vecchi, Huei-Ping Huang, et al. 2007. “Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America.” Science 316 (5828) (May 25): 1181 –1184. doi:10.1126/science.1139601.
Warshall, P. 1995. The Madrean Sky Island Archipelago: A planetary overview. In Biodiversity and Management of the Madrean Archipelago: The Sky Islands of Southwestern United States and Northwestern Mexico. General Technical Report RM-GTR-264. Tucson, Arizona: U.S. Forest Service. July.