Rehydrating Toro Creek with Sustainable Agriculture: Traceland Farm Demonstration Project

Objective 1: Water management accounting

• There are 7,000 acres of the Toro creek watershed located up stream of the Traceland agricultural well, dozens of land holders with riparian rights and hydrologically connected wells, and large variability of annual precipitation amounts as well as orographic differences. At 18 inches of rainfall on average, the reach of Toro creek that abuts Traceland is a perennial stream in several locations. Thankfully, the well has never had any issue with water supply over the last 20 years of agricultural and residential use, even during years of heavy drought. The catchment area of this rehydration project after recalibrating earlier figures post earthworks construction was determined to be roughly 40 acres. About two thirds of this drainage is detained above grade of the Traceland well in swales and basins, suggesting a potential increase in input to the agricultural well tap area.

• We assessed the consumptive water use of Traceland Farm to reduce the water footprint and off-set pumping from the agricultural riparian well. Water consumption was measured according to agricultural use based on observations and estimates for the 2023 irrigation year for a total of 3.3 million gallons or 10.17 acre-feet (af), less than originally estimated. This figure is discounted slightly from 10.42 af for the restoration plantings that have negligible consumption and will not require water after 2-3 years of establishment (Water Consumption Table).

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• Materials: Irrigation consumption table
• Methods: Accounting of water consumption

Objective 2: Expand agricultural operations onto valuable Class 1 alluvial soil agricultural land and simultaneously restore native habitat across approximately 12.5 acres,  

• • Earthworks were completed August 2023.
  • A second flower bed was developed on the Class 1 alluvial soil moving northward along the creek terrace using the grubbing and extra topsoil from the earthworks.
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• Monitoring of the terrestrial and aquatic wildlife species response to restored habitat is being continually tracked.
• Baseline began in summer of 2019 until present contains 162 observations, 149 species, 107 of which are research grade.

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    • Jesse Trace iNaturalist Observations
    •       Figure 1: iNaturalist Observations
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    • Example 1 Observations                                       Example 2 Observations
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    •  Example 3 Observations   
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  • Based on advice from the International Oak Society (IOS) and the California Conservation Corps (CCC) we decided to sow our own local and climate adapted seeds and acorns and use specialized air pruning tree pots. Change in sourcing is better quality than local nursery stock and under original budgeting cost. Plants have been germinated and are developing well. First oak grafting trials were carried out. Several native, native adjacent and non-native species were successfully grafted with the hot pipe callusing technique. This proof of concept is critical for the development of native elite oak cultivars. The nursery has grown in diversity and size and is able to supply planting efforts on Traceland as well as other ranches.
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  • Black Walnut Tray                                                      Coast Live Oak Tray                                                          Island Oak & Q. species
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• Item	Quantity	Cost
  3” x 8” air pruning pot	200	139.80
  3” x 8” pot container	8	71.92
  4” x 14”  air pruning pot	318	329.88
  4” x 14” pot container	23	265.77
  5” Plug Trays	2	116.60
  Tax + Shipping		332.30
  Total		$990.95

   Nursery Pot Costs

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• Item	Quantity	Cost
  Kellogg Potting Soil (PS)	3	35.85
  Kellogg (PS) + Peat	5+1	97.81
  Total		$133.66

   Potting Soil Costs 

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• Developed plant palette based on bioregional ecosystem mimicry: oaks, black/persian walnut, salal, huckleberry, currant, elderberry, grape, service berry, (timber, food), and found an estimate of mature oak orchard acorn production at 3.1 – 7.7 metric tons per hectare according to the book The Carbon Farming Solution, written by Eric Toensmeier, published in 2016.
• We incorporated the appropriate sizing/spacing for conservation plantings, and agro-eco rows into the design (with alleys between trees leaving plenty of space for more intensive ag and about 30 years to do it before shaded out by mature trees)
• 200 ft long 10 ft wide native food and pollinator hedgerow was established with the US-LT RCD with funding from the Wildlife Conservation Board (WCB) on the bottom most berm of the rehydration system reintroducing extirpated species and seed source according to Cal-scape distribution maps and database.
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    •                        Mature Design                                                         Spacing                                                                 Plant Palette
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      •            Conservation Row                                                          Agro Eco Row 1                                              Agro Eco Row 2

• Soil health measurements were carried out by PHD Yamina Pressler, Cal Poly Professor and soil scientist with her students in concert with the Upper Salinas Las Tablas Resource Conservation District (USLTRCD)
  • 1) soil carbon assessment – total carbon, inorganic carbon, mineralizable carbon (2) soil biological assessment – nematode community composition and abundance, and (3) soil physical properties – aggregate stability, texture, gravimetric soil moisture, bulk density (clod method)

• Materials: iNaturalist project, Graphical Soil Analysis Report
• Methods: Monitor wildlife populations and upload new species onto iNaturalist as habitat develops and soil sampling with Cal Poly

Objective 3: Reduce soil erosion and stream bank collapse 0.5 miles of Toro Creek 

• • Rehydration earthworks were completed in early August 2023. The system worked according to plan and had no issues other than minor erosion on upstream side of basins. These sluffs will be touched up summer 2024 with a skid steer.
  • Two main erosion gullies from the 100-year terrace ending in mainstream Toro creek have been located and assessed. All surface run-off was diverted effectively from the third ravine drainage via a distribution swale into the primary drainage with armored spillway. This was then terminated with an energy dissipation bowl to absorb any potential scouring force from a heavy storm. 
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  • Energy Dissipation Bowl  (EDB)                            EDB during rain 
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• Materials: Camera and 100' measuring tape
• Methods: Monitor several points systematically along the creek bank and chart evolution. 

Objective 4: Capture > 500k gal stormwater run-off 

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  • Stepped-down, on-contour berms, swales, and recharge basins were developed according to specific topography on the ground, while maintaining roughly 100 ft between the rows for mature oak tree sizing. The run-off from the 24” rain over the 2023-24 winter did not overflow from the bottom most basin spillway. During this time the system filled close to capacity on several occasions, suggesting higher than anticipated water recharge.
  • Monitoring the system, we deduced certain areas of high infiltration and potential paleo channels in some of the far reaches of the swales. We also noticed areas of high impermeability in the basin bottoms from fine silt erosion. Due to the amount of exposed soil from excavation there was significant sediment mobilization. Increased vegetative cover over time on the landscape should reduce this. There are future opportunities to utilize a keyline plow to further infiltrate runoff into the soil profile. Precaution will have to be exercised to be careful of sensitive flora and fauna recolonizing the ephemeral aquatic environment created.
  • Despite insufficient budget, observational studies and measurements were performed to estimate infiltration of detained water. The total infiltration surface area of the rehydration system is roughly 50,000 ft². A past percolation test on the 100-year flood terrace were used as a proxy to estimate water infiltration.  Results of the test were 1” of percolation every 80 min. Field observations of surface infiltration varied greatly in the features depending on location. Future funding is needed to support experts to determine infiltration relative to evaporation.
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  • • Research Question: How long does it take one inch of water to infiltrate in the rehydration system?
    • Infiltration Formula: 50,000ft2 x .082 (1 inch) = 4,100 ft3 x 7.5 gal =30,750gal per 80 min

      Infiltration Adapting Percolation Metrics

    Field Infiltration Observation:

    • In general the basin’s water surface lowered roughly 1” per day from visual observation
    • 24hrs x 60min / into 80 minutes
    • 80 minutes is 5-6 % of 24hrs
    • 5-6% of rate of perc test
    • As of May 30th, most of the basins are dry or near dry. We estimate that all features will be dry by late June 2024.

    The system most likely captured more than 500k gallons of water, though it is unclear how much was infiltrated and how much evaporated. The captured surface water attracted many different wetland species and water fowl that had never visited the site such as: redwinged black birds, blue herons, American egrets, Malards, sierran chorus frogs and benthic macronveribrates.

• Materials: Camera for routine timelapse
• Methods: Periodic photos of basins to chart evolution of system

Objective 5: Capture and bio sequester atmospheric CO2 

• • • We determined that investigating how oak woodlands and dry farmed perennial tree crop species contribute to and use groundwater was beyond the scope of this project.
    • The carbon footprint of the project’s activities was accounted for to neutralize its emissions via hardwood tree planting. Excavation of the rehydration system took longer than predicted and hence, emitted more CO2. Total workdays with two operators and two machines amounted to 18. The total CO2 emitted during the project was 72,000 kg. Including the lower sequestration rates of foreign oak trees, this project will reach carbon neutrality in 20 years from 72 oak species based on the CUFR calculations.

• Materials: CUFR Tree Carbon Calculator.    
• Methods: Calculate annual carbon average to offset earthworks emissions. 
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•                  CUFR Calculator                                                Carbon Capture

Objective 6: Research and develop acorn food production as a high-value, gluten-free, delicious flour and foodstuff.

• In December 2022, we visited the Portuguese oak dehesa agroecological farm Freixo do Meio that specializes in commercializing acorn foods as well as other woodland products. A realistic first commercial harvest was determined to be within 10-15 years of initial planting based on high yielding sweet acorn oak cultivars. A literature review has been conducted to conceptualize value-added acorn products and harvesting methods to improve efficiency of production. Acorn recipes have been developed from local species to target flavor profiles and culinary opportunities and the first steps in developing local elite oak cultivars have been taken.
• In December 2023 we visited Balanotrees near Tarragona Spain. They were very helpful in demonstrating their work-flow for vegetative propagation of elite oak cultivars. We also tried several acorns from these prized cultivars and were impressed with their size, shelf life and delicious flavor of the acorns.
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•          Acorn Recipe Experiments
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• Materials: 5 Gallon Bucket, Nut Wizard, Scale
• Methods: Gather acorns from local trees, leach and taste test in various recipes. Visit and taste test acorns from European leaders.