The Waterman Restoration Project

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An 18-acre saguaro/palo-verde bajada on BLM land was bladed by a mining claimant (1980–1997) and subsequently infested with a monoculture of buffelgrass. Volunteers worked with BLM to suppress the buffelgrass and bring back native plants (133 species) by carefully spot-spraying the buffelgrass and allowing the native plants to emerge and thrive. Over a 16-year period, simple water harvest structures (>150) were constructed by volunteers and tree branch mulch (>300 truckloads) was brought in to cover bare soils. Native tree species were seeded by hand and in recent years young saguaros are being transplanted into the site.

18Acres

133Native species

2,000+Trees established

7,000+Volunteer hours

75+Saguaros transplanted

Fixed Point 2011 — Fixed Point 3 — 2011.

Fixed Point 2016 — Fixed Point 3 — 2016.

Fixed Point 2021 — Fixed Point 3 — 2021.

Contouring the Slope & Planting Desert Tree Seeds

In June 2010 a BLM team of large machinery operators ripped the entire 18 acres along contours to fill in erosion channels and form contoured terraces. Immediately following that work, volunteers harvested nearby desert tree seed (Whitethorn Acacia, Foothill Palo Verde, and Ironwood) and hand-planted the seed during the months of July and August 2010. Volunteers have continued to harvest and plant seed every year to fill in gaps where trees had not emerged.

By 2016 there were over 2,000 established desert trees on the 18 acres. All restoration trees were planted from seed and no trees were ever irrigated. By 2026 some of the trees planted in 2010 are 15 feet tall.

Contoured furrows ripped by BLM heavy equipment, June 2010 — Contoured furrows ripped by BLM heavy equipment — June 2010.

Volunteer planting tree seeds in July 2010 — Volunteer planting of tree seeds in July 2010.

Volunteer planting tree seeds — Volunteer planting of tree seeds over the years.

Foothills Palo Verde and Ironwood seedlings — Foothills Palo Verde seedling (right) and Ironwood seedling (left).

The Long-Term Buffelgrass Control Effort

With the onset of monsoon rains in July 2010, the entire 18-acre site was like a golf course of buffelgrass turf by mid-August. A team of 3 to 5 volunteers spot-sprayed buffelgrass three times weekly from the first week of August through mid-October 2010. Multiple passes were made following the mantra of “spraying the bad guys and leaving the good guys.” Ongoing spot spraying continued every season with monsoon and winter rains. Since 2022 we are finding fewer than 150 plants per season.

The exhaustion of the buffelgrass population was rapid. In 2010 we applied a total of 234 gallons of herbicide, in 2011 74 gallons, in 2012 45 gallons, and 2013 10 gallons. Since 2015 we have annually applied 3 to 5 gallons per year depending on the rainfall and size of the plants.

The initial buffelgrass monoculture sucked most of the surface moisture from the site and deprived it from native plant growth. As we removed the buffelgrass, the soil moisture became increasingly available for native plant growth.

Herbicide volume applied each year — sharply declining trend — Annual herbicide applied to the restoration site — a steep, lasting decline.

Native plants returning where buffelgrass was sprayed — Persistent buffelgrass elimination makes way for more native plants.

Baby tortoise found among buffelgrass — Finding a baby tortoise among the sprayed and unsprayed buffelgrass.

Buffelgrass growing inside a native nurse plant — Buffelgrass often grew inside native nurse plants.

Stray buffelgrass plants that escaped notice are still being found.

Keeping Rainwater on the Site

The restoration is situated on the foothill slope of the Waterman mountains with grades up to 6%. Rainwater flows onto the site from hillsides above and is also collected over the 18 acres. An extensive network of one-rock dams and rocked waterways has prevented the downcutting of erosion channels. One-rock dams are only one rock deep and designed to slow rainwater flow and spread it out laterally to soak into the soil. As plants have proliferated and grown, even high-volume rainwater stays entirely on the site and none of it runs off.

The mining claimant had spread thick layers of compacted gravel over his residential site. That deep compacted gravel prevented most native plant emergence. We hired a backhoe operator to dig “water retention dimples” over a 2-acre area. Within one year, native plant life and planted tree seeds emerged and developed.

One-rock dams five years later, with vegetation.

Water retention dimples made by backhoe in deep compacted gravel.

Tree Branch Mulch

The desert soil surface had been scraped by the mining claimant and later disturbed by the BLM heavy-equipment soil ripping. Large areas over the site remained bare without vegetation after two years. We discovered that tree branches spread over those bare areas provide enough shade and residual soil moisture to support the emergence of both annual and perennial plants. The effect of tree branch mulching has been remarkable. The decaying tree tissue coupled by emergence and growth of native plants quickly bring life back to the soil and enhances rainwater absorption. We were careful not to bring in tree seeds of species that were not already growing on the restoration site (no mesquite, blue palo verde, or exotic seed).

Volunteers dragging branches — We organized several “drag parties” to spread branches.

Branches providing shade and moisture — Branches provide shade that prolongs surface moisture and promotes growth.

Mulch stimulating new plant life — Tree branch mulch stimulating new plant life on bare soil.

Annual natives under branches — Annual native plants taking root under tree branches.

Using Christmas Trees to Heal a Massive Erosion Channel

In September 2022 a freak 3.5-inch rain event opened up a 500-foot channel 3 feet wide and 3 feet deep along the flank of the upper restoration site. In January 2023 volunteers packed discarded Christmas trees end-to-end in the channel. The Christmas trees stopped all runoff down the channel during monsoon 2023. In January 2024, 2025, and 2026 volunteers packed additional trees into the channel to reinforce the integrity of the decaying anti-erosion Christmas-tree mulch. In just four years the channel is gradually filling in and starting to meander.

Erosion channel before Christmas-tree packing — The 500-foot channel opened up by the September 2022 storm.

Volunteers packing Christmas trees in the channel — Volunteers packing discarded Christmas trees end-to-end.

Channel filling in and starting to meander — Four years on: filling in and starting to meander.

The Return of the Natives — 133 Native Species and Counting

We hand-seeded native tree species continually between 2010 and present. Many of the older trees have started to flower and produce seed on their own. In addition to the desert trees we have also broadcast-seeded Ocotillo.

Other than desert trees and Ocotillo we did not seed or transplant any other desert species. We did not plant any seed mixes. A total of 133 native species have emerged from the soil seed bank or from seed blown in from adjacent desert areas. Twenty-one of the 133 natives are grass species.

Foothill Palo Verde tree — Foothill Palo Verde Tree.

Whitethorn Acacia tree — Whitethorn Acacia Tree.

Three Early-Pioneer Species

Three species were key early pioneers that have had significant impact on providing early soil coverage and shade to nourish newly emerging native plants.

Fluffgrass (Dasyochloa pulchella)

This tiny, unnoticed grass less than 6 inches tall is one of the first species to emerge in disturbed soils in the desert. It quickly spreads by seed and when there is enough moisture it produces runners with little plantlets. After only two years of growth it gracefully dies and leaves behind abundant plant litter that catches seed of blowing native plants.

Trailing Four O’Clock (Allionia incarnata)

This showy-flowered annual plant is remarkably opportunistic in its ability to germinate after even light rain showers. It emerges and remains hunkered down until there is sufficient moisture for growth to resume during the monsoon season. In wet years it can send out runners up to 15 feet covering the surface in carpets of showy pink flowers. At the end of the season it gracefully dies and its litter provides shelter for other species to later emerge. It also provides habitat for insects and rodents.

Mexican Panicgrass (Panicum hirticaule)

This annual grass emerges in August and is especially abundant wherever buffelgrass has been sprayed. In early stages this grass strongly resembles buffelgrass.

Fluffgrass as a pioneer — Fluffgrass in action as a pioneer on disturbed desert soil.

Trailing four o'clock extending runners — Trailing four o’clock extending new runners.

Mexican panicgrass amid dead buffelgrass — Mexican Panicgrass amid dead buffelgrass.

Two Climax Keystone Species

Two climax keystone species are gradually dominating the restored flora.

Foothill Palo Verde (Parkinsonia microphylla)

The constant companion of saguaros, especially on desert slopes (bajadas). Foothill palo verdes are the principal saguaro nurse plants and tolerate the same levels of stress as saguaros. These trees provide umbrage to numerous desert shrubs and cacti, and nesting habitat for verdins and black-throated sparrows.

Triangleleaf Bursage (Ambrosia deltoidea)

One of the keystone plants of the Upland Saguaro–Foothill Palo Verde subdivision of the Sonoran Desert. In undisturbed desert it is the major sub-brush species. It lives for 50–70 years and is drought-deciduous: under mild drought it drops its leaves; under severe stress it drops its branches. Over the decades it provides significant plant litter to the soil thereby building up soft soil texture underneath it. The soft soil facilitates burrowing by rodents that in turn promotes water absorption into the soil during monsoon and winter rains. The extensive coverage of triangleleaf bursage on desert floors is key to capturing rainfall water and avoiding soil erosion. Triangleleaf bursage quickly succumbs to buffelgrass infestation. Getting buffelgrass under control on this restoration site has resulted in a healthy population of triangleleaf bursage that is gradually expanding throughout the restored areas.

Foothill palo verde with bursage understory — Foothill palo verde sheltering a bursage understory.

Bursage and palo verde colony — An expanding bursage and palo verde colony.

Verdin nest in foothill palo verde — A verdin nest sheltered by palo verde branches.

Bursage rebounding after buffelgrass removal — Bursage rebounding where buffelgrass once dominated.

Foothill palo verde in bloom — Foothill palo verde in spring bloom.

Getting Saguaros Established

In 2012 BLM granted AZNPS volunteers permission to harvest saguaro fruit on Ironwood Forest National Monument for the purpose of sowing the seed on the restoration site. We harvested fruit and sowed seed under young desert trees over 8 years. Up to now only one saguaro plant has been found growing under a brittlebush plant.

In 2021 AZNPS signed an agreement with the Tucson Cactus and Succulent Society whereby TCSS would donate small salvaged saguaros to AZNPS to transplant under desert nurse plants on the Waterman Restoration. By 2026 over 75 saguaros have been transplanted.

Transplanted saguaro under a nurse plant — A transplanted saguaro under its desert nurse plant.

Placing protective cage over transplanted saguaro.

Recovering saguaro under protective cage.

The 100-Ton Sponge Demonstration Garden

A passive water-harvest garden was designed by AZNPS volunteer Dennis LeBlond in 2017. Twenty tons of railroad-ballast coarse rock was overlayed with 80 tons of desert soil and rock. The garden was built on a slope-and-swale area that allowed rainwater to be absorbed into the structure, stored in the railroad-ballast layer, and wicked up by the drier desert soil above.

Desert tree and ocotillo seedlings were planted from deep pots and hand-watered through perforated watering tubes for a period of a year before being removed. Desert grasses and forb species were planted by seed and have emerged following rainfalls. The demonstration-garden signage is maintained by volunteers and moved around as plants die and new plants emerge.

Railroad ballast with first load of desert soil, 2017 — Railroad ballast with the first load of overlayed desert soil, 2017.

Desert soil and large rock flanks, 2017 — Overlayed desert soil and the first large rock flanks, 2017.

Demonstration garden in 2018 — The Demonstration Garden in 2018.

Demonstration garden in 2019 — The Demonstration Garden in 2019.

Demonstration garden in 2022 — The Demonstration Garden in 2022.

Over 7,000 Hours of Volunteer Work

A core group of 3 to 5 AZNPS volunteers provided continuity, direction, and coordination over the 12 years of restoration. In addition to the core AZNPS group, BLM interns have provided timely assistance at crunch times.

A dedicated core volunteer group from the Dove Mountain Hiking Club provided invaluable manpower to the initial seeding and buffelgrass spray efforts.

We organized the annual Waterman Restoration volunteer workday the first Saturday of December. Typically there were between 40 and 50 volunteers split into seven groups of up to seven volunteers. Several tons of rocks were moved to build water-harvest features on those workdays.

There have been fourteen Eagle Scout projects in which groups of 15 to 30 scouts and family members provided significant effort in focused areas. Most of the projects were dedicated to construction of one-rock water-harvesting dams and tree-seed planting.

UA student clubs and ASDM youth clubs also provided workday efforts building one-rock water-harvest features.

Since 2023 a core dedicated AZNPS group of volunteers regularly stewards the restoration site by amending tree branch mulch, repairing erosion channels, seeding new trees where needed, and transplanting saguaros.

UA Soil and Water student club at work — UA Soil and Water student club laying out a contour for a one-rock dam.

ASDM Club members learning water harvesting — ASDM Club members learning about water harvesting.

Volunteer preparations on annual December workday — Volunteer preparations on an annual December workday.

Annual Fixed-Point Photography, 2011–2025

Six fixed points were selected in Fall 2011 to record annual vegetation differences.

At exactly the same time of day around 15 October every year, photographer Jim Cowlin took pictures of the identical scene at each of the six photo points.

Below are the six views — use the prev/next buttons or the year chips beneath each frame to scroll through fifteen years of change.