New Mexico Water eNews

Land Use Analysis for Acequia Irrigated Valleys
by Robert Sabie, Jr., Research Assistant

Within the traditional irrigated valleys of New Mexico, water from streams and rivers is diverted into unlined irrigation ditches referred to as acequias. Gravity flow distributes the water to agricultural fields from the acequias through a series of lateral ditches. The management of the diverted water is implemented at a local level and requires cooperative community efforts to maintain the irrigation system. While these acequia systems have been in place for several hundred years, the last 70 years have seen many changes in land use and community structure.

Land use, referring to the human use assigned to an area of land, firmly connects the community social fabric and the hydrologic cycle within acequia irrigated valleys. Prior to World War II, the land in these valleys was used primarily for small-scale farming and ranching. Since the end of the war, much of the land has changed from irrigated agricultural uses (i.e., alfalfa, orchards, and row crops) to non-irrigated uses (i.e., long-term fallow, roads, and development). Along with the changes in land use came changes in community demographics and lower participation in the cultural traditions of acequia irrigation. Less irrigation in these valleys also affects the hydrologic cycle. Changes in water quality, water quantity, shallow groundwater recharge, evapotranspiration, nutrient transport, and surface runoff are often associated with changes in land use.

Staff at NM WRRI are using current and historic aerial imagery to digitize land use for three acequia irrigated valleys in Northern New Mexico. The first step in the process involves creating digital versions of older images by scanning them with a large scanner. The images are then geographically referenced to a previously referenced high resolution image using identifiable features from both images. Boundaries are drawn around the areas of land use and each area is classified using aerial photo interpretation techniques. The result is a continuous surface of land use within each valley for each year being examined as shown in the figure. The land uses can then be quantified and analyzed.

Several research projects currently are being conducted by WRRI partners in collaboration with members of three acequia communities in Northern New Mexico. One project is using a time series of aerial photographs taken between 1934 and 2014 to examine the relationships between changes in land use, water availability, and socioeconomics. Three studies conducted by graduate students at New Mexico State University are using the most current land-use data for examining evapotranspiration, soil moisture, and creating a water budget model. These research projects will help in understanding the dynamics between human and natural systems in order to improve community resilience during times of drought.

The Transport and Accumulation of Pyrogenic Black Carbon in Fire-prone Watersheds and Implications for Water Quality
by Daniel Cadol, Amy Galanter, and Phoebe Nicholls, New Mexico Tech

Post-wildfire debris flows and flooding deliver abnormally high loads of sediment to downstream hillslopes, floodplains, and waterways. In addition to the mineral sediment, black carbon (BC) in the form of soot and char generated by incomplete combustion of organic matter is transported and redeposited throughout the watershed. Black carbon has the potential for negative impacts on water quality during transport, for example, fouling of drinking water supplies, and generation of anoxic conditions. But when incorporated into soils, it may also have positive impacts, such as sorption of contaminants and carbon sequestration. The primary goal of this project was to better understand the transport processes that control the accumulation locations of pyrogenic debris such as ash and char. To do so, we quantified the soil BC content in various geomorphic settings in two recently burned areas in the Jemez Mountains (the 2011 Las Conchas fire and 2013 Thompson Ridge fire) and one nearby control watershed before and after the monsoon season of 2013. We also quantified the soil BC content pre- and post-wildfire at 24 sites that had been sampled prior to the Thompson Ridge fire. The secondary goal of this project was to understand the environmental effects of BC in regards to sorbing and sequestering potential contaminants. To achieve this goal we quantified the capacity of several depositional zone soil samples (with and without artificially augmented char content) to absorb the heavy metal arsenic. We quantified the natural load of sorbed As, Pb (both present), and Cr (not present) in depositional zone samples from our study area, and ongoing work will examine sorption of Cr.

Analysis of the soil samples from the two fires and the control site yielded a significant negative relationship between time since burn and black carbon content in the upper 10 cm. Floodplain soil soot content indicated delivery of additional BC downstream of both fires during the 2013 monsoon season. Hillslope BC redistribution on the north-facing hillslopes during monsoon season showed decreases on the upper slope and increases near the toe of the slope, consistent with downslope transport by runoff, however the south-facing hillslopes analyzed did not show this movement. From this first data set we tentatively conclude that BC is relatively mobile, and is dominantly transported by runoff and floods over short time scales following fire. The pre- and post-fire samples reveal a much more complex system. The subsurface samples (5-15 cm below the surface) frequently varied pre- to post-fire, but there was no discernable trend. We suspect heterogeneity in the soil and the inability to resample the exact same location contributed to this result. The surface samples also showed both increases and decreases in BC content following the fire. There was a trend toward BC decreases in upslope areas and BC increases in downslope and floodplain areas. We suspect that erosion removed BC in steep areas and deposition augmented BC in lower energy areas, but geospatial and landform analyses are ongoing.

In the sorption studies, adding black carbon to floodplain soil samples slightly increased the amount of arsenic sorbed for each sample and greatly decreased time to equilibrium. The sorption isotherms for the floodplain and hillslope soils follow a generally linear Fruendlich pattern, though the sorbents involving added char gave inconclusive results. We found evidence of competitive sorption from our batch equilibrium tests in that the Pb content of the solution spikes following As addition and then declines over the following days. Leeching tests indicate As and Pb are already present in the soils and desorb from them, not surprising given the volcanic history of the study area. In contrast Cr was not found, making it an interesting target for ongoing work. The clay and pre-existing BC content of the soils appear to be more than adequate to sequester the naturally occurring chronic As loads, but additional post-fire BC does increase the capacity measurably and may be important in instances of acute contaminant release.

“Every Drop Counts” Activity Draws Hundreds at Annual Las Cruces Water Festival
by Celeste Prieto, Student Assistant

The Las Cruces Water Festival is an annual event sponsored by the City of Las Cruces. This event hosts third and fourth graders from public schools throughout the region. The 2015 Water Festival was held at Young Park in Las Cruces and drew about 1,500 students to the day event. At the Water Festival, science exhibits, information booths, and fun, interactive activities were presented by local companies and institutions to the visiting students to educate them on the importance of the water cycle, water conservation, and the role the community plays in obtaining, maintaining, and protecting water resources.

The New Mexico Water Resources Research Institute presented a booth that featured a game called “Every Drop Counts,” an activity designed to teach students about the importance of water conservation. The object of the game was to transfer water from a full bucket at one end of a line to an empty bucket at the other end by passing a cupful of water at a time down each line, from student to student, without spilling any water. Students quickly discovered that it was not only about which team could fill the empty bucket the fastest, but also which team could preserve the most water in the process. Students also learned that, because the water being used in the game was being recycled for each group of students, preserving the water was crucial. The activity provided the students with a visual representation of how joint community effort through cooperation can directly correlate to water conservation.

After the “Every Drop Counts” game was played, students proceeded to the NM WRRI presentation booth where they were asked questions about what they thought the game represented, what they knew about the water cycle, why water conservation is important, and how they felt they could preserve water in their own everyday lives. After the presentation, students were given colorful activity booklets to provide an additional interactive way to better understand the importance of the water cycle and water conservation. Students then concluded the activity by filling in their “passports” (booklets with specific learning objectives given to each student at the beginning of the water festival) with information they obtained from the NM WRRI game and presentation.

NM WRRI Research Assistant Presented Award
by Catherine Ortega Klett, Program Manager

This spring NM WRRI research assistant Robert Sabie received the  2015 James J. Parsons Award for Excellence in Thesis Research from the New Mexico State University Department of Geography. The award was established by Dr. Jack Wright to honor Dr. Parsons, who was one of the world’s most honored cultural geographers. This award is given annually to a student whose research is in the area of cultural geography, has high marks in geography coursework, and who has a personal commitment to environmental conservation and cultural sensitivity.

Robert has worked on various research projects that are grounded in environmental conservation and cultural sensitivity since he was an undergraduate at Western Washington University. The idea for his master’s thesis research on remote sensing of surface coal mine reclamation in drylands came from his work with a group advocating for Navajo environmental justice. At NM WRRI, he is using his geography skills to assist researchers examining the relationship between land use, evapo-transpiration, and soil moisture in traditional acequia communities in Northern New Mexico. Robert says, “I look for the cultural elements in every research project I am involved in. I enjoy helping communities and I think of help as struggling together. I see geography as a platform to help solve problems because it uses both qualitative and quantitative methods. Many research projects focus strictly on quantitative analysis. Adding a cultural or participatory element can really make a project more meaningful and useful to a community.”

NMSU Assistant Professor KC Carroll Named Outstanding Reviewer in Barbados
by Catherine Ortega Klett, Program Manager

New Mexico State University Assistant Professor KC Carroll of the Plant and Environmental Sciences Department has been awarded Outstanding Reviewer status by Elsevier’s journals. Dr. Carroll was awarded this honor as he is in the top 10^th percentile in terms of the number of reviews he has completed for the Journal of Contaminant Hydrology in the past two years.

In addition to his faculty duties in the College of Agricultural, Consumer and Environmental Sciences, Dr. Carroll is conducting research on the spatiotemporal groundwater level changes throughout New Mexico for the NM WRRI’s Statewide Water Assessment. He has served on NMSU’s Water Science and Management (WSM) Steering Committee since he joined the university in 2013. The WSM is an interdisciplinary degree program for masters and doctoral students interested in becoming water professionals as water resource researchers, educators, and managers. Dr. Carroll assists with the graduate student admissions process and contributes to administrative decisions for the popular graduate degree program.