Orchard Rain and Snowmelt Harvesting Plan

Prairie Plants · Ideas from Brad Lancaster's Rainwater Harvesting for Drylands and Beyond (Vol. 1, 3rd ed., and Vol. 2, 2nd ed., both 2019), adapted to a snowy site with dry summers

Companion page; it does not change the planting or pollination plans. Tree positions use the current canonical planting records in orchard_pollination_grid.html. Slope from USGS 3DEP lidar, the same data as the whole-site maps: the homestead is the high ground, the land falls north and west to the low northwest corner by the road, and the planted block sits at the south end of the 600 ft strip, R1 about 15 ft inside its south line. Climate from PRISM 1991–2020 normals and ERA5 reanalysis (see Sources and Assumptions).

The Plan in Brief

PRISM puts Prairie at about 22 in of precipitation a year, about double the ~11 in often quoted for Elmore County, which reflects the low desert around Mountain Home. NRCS lists 12–16 in for your soil's setting, so your lot may get less; a rain gauge will settle it. Either way it's more than Lancaster gets in Tucson. The catch is timing: about two-thirds falls from November through March, and about half of the year's total arrives as snow while the trees are dormant. July through September brings only about an inch, just when a mature orchard's demand peaks. The plan:

Start at the top. The homestead roofs and gravel pad sit at the high point just south of the orchard. Catch their water and spread it into the top rows.
Catch it where it lands. A basin at every tree soaks snowmelt and spring rain deep, filling the soil "tank" before summer.
Pass the overflow downhill. Each basin spills to the next tree, and the chain ends in a sponge basin at the low northwest corner by the road.
Let the drip fill the July–September gap. Harvested water won't replace the drip, but it can delay the first run, shorten the season, and soften dry spells.

Water In vs. Water Demand, by Month

Bars: PRISM 1991–2020 normal precipitation (inches of water) at Prairie. Line: FAO-56 reference evapotranspiration (ET₀) from ERA5, 1995–2024, the water a well-watered grass surface would use; mature trees with full canopies use a similar amount per area of canopy, young trees far less. In the shaded months the mean temperature is below about 36 °F, so most of that precipitation arrives as snow.

The Land: Lidar Contours and Flow Paths

Whole field, north up like the site maps

From USGS 3DEP lidar fitted to the fences (331 × 1,292 ft), shared with the whole-site terrain and water maps. Contours are 1 m (3.3 ft) apart, labeled in meters. Blue lines are where runoff from a tenth of an acre or more gathers; south of the green split line the lot drains south, away from the orchard. The shed, containers, pump house, 3,500 gal irrigation tank, and house pad are placed from the site master grid (drone photos, October 2026).

The Soil: Simonton Loam and How Water Moves Through It

USDA NRCS Web Soil Survey report for the property: map unit 149, Simonton loam, 2 to 12 percent slopes (Elmore County Area, Idaho, survey version 14, August 31, 2026), with layer data from NRCS Soil Data Access. Owner: no rock on the property and about 10 ft of soil before rock.

Typical profile, to scale

Layer	Depth	Texture	Clay	Soaks in, in/hr	Holds, in per ft	What it means for water

"Soaks in" is NRCS's saturated hydraulic conductivity (Ksat), typical value with the low–high range; "holds" is available water capacity, the water roots can use. Hydrologic soil group C; well drained; no flooding or ponding; no water table or restrictive layer within 80 in.

Water-Harvesting Site Plan — To Scale, South Up, West Fence on the Right

Same orientation as the planting map (the view from the north end looking south), so the homestead, the high point, is at the top and the road, the low end, is at the bottom. Distances are from the west fence and the R1 row line. Hover over a tree for its position.

Techniques by Zone, Top of the Slope to the Bottom

Lancaster's second principle: start at the top of the watershed and work down. Book references are chapters in Volume 1 (3rd ed.) or Volume 2 (2nd ed.).

Zone	What to build	Size and specs	Book	When

Lancaster's Eight Principles, Applied Here

#	Principle (Lancaster's wording)	On your site
1	Begin with long and thoughtful observation.	Walk the block during snowmelt and after summer storms. Flag where water runs and ponds and where snow and frost linger, and use the log on the last page.
2	Start at the top (highpoint) of your watershed and work your way down.	Your high point is the homestead pad: its roofs and gravel come first, then the driveway and the top rows. The northwest corner by the road comes last.
3	Start small and simple.	One crescent per tree: at planting for new trees, and as soon as you can for the trees already in the ground. Add the spreader, driveway basins, lane, and corner basin after a season of watching.
4	Slow, spread, and infiltrate the flow of water.	Level basin floors and level berm crests; many small basins instead of one ditch; mulch everywhere water lands.
5	Always plan an overflow route, and manage that overflow as a resource.	Every basin spills to the next tree downhill, and the chain ends in the northwest sponge basin, not the road.
6	Maximize living and organic groundcover.	Wood chips in the basins, perennial cover in the alleys, clippings blown onto the rows.
7	Maximize beneficial relationships and efficiency by "stacking functions."	The windbreak is also a snow fence, a nut crop, and a mulch source; the berry guilds sit in the drift zone; elderberry cuttings plant the sponge basin; roof tanks double as gravity-fed drip.
8	Continually reassess your system: the "feedback loop."	Each fall, widen basins toward the drip line and fix spots where water broke through or stood too long.

Crescent Berm 'n Basin at Each Tree

Plan view, oriented like the site plan (south up, west on the right)

Section down the fall line (uphill on the left), drawn to true scale

Build it as you plant

Plant on a low mound, 3–4 in high and wider than the root ball, so the root flare ends up 1–2 in above the future spillway level after the soil settles. (The fall 2026 trees are already planted, so start at step 2 for them.)
Find the downhill direction at the tree with a level. Expect northwest in R1–R5 and north-northwest farther north (the site plan shows each tree), but local bumps rule.
Mark an arc on the downhill side, 3–4 ft from the trunk, with its ends running along the contour and curving slightly uphill.
Shape a shallow, level-floored saucer between the mound and the arc, digging no deeper than about 2 in so the floor stays in the loam above the stickier clay-loam subsoil. Get the rest of the depth from the berm: pile soil on the arc (scrape extra from the alley side, never from the basin floor), tamp it, and level its crest.
Cut a spillway notch in the middle of the berm so water can stand 3–4 in deep at most (3 in or less for stone fruit), with the crest 2–3 in higher. You don't need rock: line the notch with a strip of sod from the alley, or a paver or board set flush, so overflow can't cut it. Aim it at the next tree downhill, usually the northwest diagonal about 22 ft away (the site plan shows which).
Mulch the basin with 2–3 in of wood chips (about 2 in for stone fruit), keeping the chip surface at least 1 in below the spillway and a 6–12 in bare ring around the trunk, and add a hardware-cloth guard.
Set the drip emitters inside the basin under the outer canopy, and move them outward as the tree grows.
Test with a hose or the first storm. Water should spread along the berm, not pour out one end, and soak in within about a day.
Each fall, extend the arc outward toward the drip line.

Find the contour

An A-frame level, a water level (clear tubing filled with water), or a laser level all work; Volume 2, Appendix 1 covers all three. With an A-frame, mark where the plumb line crosses the crossbar, flip the frame end for end on the same two spots, and mark again; halfway between the marks is level. Then walk the frame across the slope, swinging one leg until the line hits the level mark, and flag each foot. The flags trace a contour. On your ground, expect contours to run east-northeast to northeast, crossing the tree rows at about 17–56°.

Test how fast your soil drinks

Dig a hole about 12 in deep and 8 in wide near the south end, the middle, and the northwest part of the block; its sides also show where the stickier clay loam starts. Fill it, let it drain, refill it, and measure how far the water drops in one hour. NRCS rates the clay-loam subsoil at about 0.4 in per hour (0.2–0.6), so 4 in of water should be gone in about 10 hours (7–20). For a basin to empty within about a day, keep its water depth no more than 24 times your hourly drop. Where water still stands after a day, send extra water only to wet-tolerant plants.

Who Gets the Water

Counts and positions come from the current planting records, including the planted M-111 rootstock; vacant spots and outside-orchard trees are excluded. Wet-soil tolerance follows UC IPM's fruit site-selection guidance; canker notes follow the inventory flags shown on the pollination grid.

Fruit	Where · trees	Wet-soil tolerance	Basin	Send overflow?	Notes

Cold air follows the water. On frosty spring nights cold air drains the same way water does, toward the northwest corner by the road. With the block at the south end of the strip, that open corner, about 300 ft past R15, is the frost pocket, not the orchard. Within the block the stone fruit (R9–R12) is on the lower half but on its steepest band, so cold air keeps moving, and the apricots (R11–R12, C1–C3) and the plums at R12-C5 and R12-C6 are the lowest planted trees. Stone fruit blooms first, and UC IPM notes that bacterial canker, already flagged on many of these trees, is worse in low spots and after spring freezes; drought stress and irrigation that wets the trunk also set trees up for it. So these trees need water that soaks through, never water that stands, plus steady drip in summer. Don't plant a solid hedge across the block's north end, where it would dam cold air against them. NRCS lists only 60–100 frost-free days for this soil's setting, so that cold-air drainage matters.

Row-by-Row Build Tracker

Row	Trees in the plan (west to east)	Basin	Crescents shaped	Chips + guards	Drip in basins	Notes

Water Budget (Lancaster's Formula)

Gallons = area (sq ft) × inches of precipitation × 0.623 (Vol. 1 Ch. 2 and App. 3). These are gross volumes, before runoff, evaporation, and snow sublimation; the earthworks exist to keep more of it on your ground. They use PRISM's 22 in; if your gauge shows NRCS's 12–16 in, multiply by about 0.55–0.75.

Catchment	Area, sq ft	Gal per inch	Gal per average year	Nov–Mar	Apr–Jun	Jul–Sep

Your homestead catchments (type in the areas)

Measure each roof's footprint including the eaves, and the pad. The runoff factor is the rough share that runs off: about 0.9 for metal roofs and 0.5 for compacted gravel; edit to suit. March through June is the tank-filling season; the year total is gross.

Catchment	Area, sq ft	Runoff factor	Gal per inch	Gal Mar–Jun	Gal per year

Summer gap for one mature tree (rough)

On one tree's 18 × 20 ft space	Inches	Gallons

Season-by-Season Calendar

When	What's happening	Water-harvesting work

Sources and Assumptions

Brad Lancaster, Rainwater Harvesting for Drylands and Beyond, Vol. 1, 3rd ed. (Rainsource Press, 2019): eight principles (Ch. 1), site water budget (Ch. 2), earthworks and cistern overview (Ch. 3), "Raised Paths, Sunken Basins" (Ch. 4), calculations (App. 3), windbreaks and snow-drift harvesting (App. 8).
Brad Lancaster, Rainwater Harvesting for Drylands and Beyond, Vol. 2, 2nd ed. (2019): infiltration basins (Ch. 2), berm 'n basins including "Harvesting Windswept Snow" (Ch. 3), infiltration trenches (Ch. 5), mulching (Ch. 7), hardscape runoff (Ch. 8), diversion swales including "Snow Diversion Berms" (Ch. 9), greywater (Ch. 12); water, A-frame, and laser levels (App. 1).
Brad Lancaster, Water Harvesting Principles (wording of the eight principles).
PRISM Climate Group, Oregon State University: 1991–2020 monthly normals, 800 m grid, sampled at Prairie (43.50° N, 115.57° W): about 22 in a year.
Open-Meteo Historical Weather API (ERA5 reanalysis), 1995–2024 at the same point: FAO-56 reference evapotranspiration, and about 52% of precipitation falling as snow.
Idaho Department of Water Resources, Adjudication Memorandum #11, Private and Diffused Waters: a landowner may use diffused surface water from rain and melting snow before it enters a natural channel (even one that flows only in spring), unless intercepting it measurably injures a prior water right.
UC IPM: Bacterial Canker (cherry), worse in low or sandy spots, after spring freezes, and with drought stress or irrigation that wets the tree; Site Selection (Fruit), pears tolerate wet soils better than other fruit trees, while cherries and peaches cannot tolerate saturated soil; Phytophthora Root and Crown Rot, avoid prolonged saturation or standing water at the base of trees.
USDA NRCS Web Soil Survey report for the property (soil folder): map unit 149, Simonton loam, 2 to 12 percent slopes, Elmore County Area, Idaho (version 14, August 31, 2026); layer data (Ksat, available water, clay) from NRCS Soil Data Access.
CoCoRaHS: volunteer network that measures daily rain and snow at home with a standard gauge.
Terrain: USGS 3D Elevation Program (3DEP) 1 m lidar, fitted to the fence lines on USGS NAIP imagery (331 × 1,292 ft fence to fence) and smoothed to about 5 ft; contours, flow paths, and slopes come from that surface, the same data as the whole-site maps (data/site_terrain.js). Bumps smaller than about 5 ft don't show. An earlier version of this page traced the owner's USGS 1 m contour screenshots; across the planted block the two agree within a degree of fall direction and about 0.1 ft per 100 ft of grade. Both replace the earlier field estimate (about 25 ft of fall to the north over 600 ft and 5–10 ft to the west): the north fall in the strip is closer to 10 ft, and the west tilt is about as strong.
Block placement (owner's choice, October 6, 2026): R1 about 15 ft inside the south line of the 600 ft orchard strip, which is taken to start at the north fence, so R15 is about 305 ft from the road.
Plan geometry (pollination grid snapshot, October 4, 2026): offset grid of 18 ft by 20 ft, C1 trunks 38 ft from the west fence, 35 ft windbreak (mulberry 5 ft and hazelnut 20 ft from the fence), alley 25–32 ft, orchard plot 35–272 ft, driveway 300–322 ft, east fence 332 ft with the elderberry hedge 5 ft inside it. The planted block is taken as 237 × 300 ft.
Rough factors: a mature semi-dwarf tree uses about 0.8 × ET₀ over its 360 sq ft and roots 3–4 ft deep; the soil tank uses the Simonton layer values, about 6.4–8.1 in of available water in that depth. The owner reports no rock and about 10 ft of soil to rock.