Water

Eight views of water on the property — rainfall, runoff, the watershed it sits in, and the rainwater-harvesting potential across every surface.

Precipitation by Month

Monthly precipitation normals for the design site. Rain is spread evenly across the year — there is no dry season (Köppen "f") — so the rainwater-harvesting case is not drought relief. It is (1) the mid-summer stretch when garden evapotranspiration outpaces rainfall, and (2) capturing the roughly 25 % of rainfall that currently runs off the lot to the Freestone Avenue storm drains.

Annual total 43.5 in Monthly mean 3.6 in Wettest Jul, 4.25 in Driest Feb, 2.81 in 100-yr 24-hr 8.09 in
Monthly precipitation, inches
12-month normals · dashed line = monthly mean (3.6 in) · shaded = peak garden-ET window

Reading it for water design: every month clears 2.8 in, so cisterns are rarely bone-dry — but July–September combine the highest air temperatures with only average rain, and that is when the Zone 3 vegetable garden runs short. A single average month (~3.6 in) sheds roughly 9,000 gal off the site's ~2,475 ft² of roof + pavement; the design aims to slow, spread, and sink that rather than lose it to the street.

Source: monthly normals digitized from the Lesson 1 Climate Survey (PDC Pro Figma Slides, June 2026; sourced there via WeatherSpark / NASA POWER), same series used in lesson-01-climate/assets/climate-survey-charts.html. Design-storm depth (100-yr 24-hr) from NOAA Atlas 14 Vol. 10, point 41.573, −72.634.

Runoff by Surface

Estimated average-year runoff from every surface on the 0.43-acre lot. Runoff = area × 43.5 in/yr × runoff coefficient. Blue = hard (roof, pavement); green = permeable (turf, beds, woodland).

The lawn sheds more runoff than every roof, the driveway, and the walks combined. ~16,100 ft² of turf and planting at low coefficients still produces ≈68,000 gal/yr; all ~2,500 ft² of hard surface produces ≈61,000 gal/yr. Building soil sponge and shrinking lawn cuts runoff more than any tank.
The share flip — area vs. runoff
Permeable surfaces are 87% of the lot's area but only 53% of its runoff; hard surfaces are 13% of area but 47% of runoff.
Average-year runoff by surface
gallons per year · bar label shows area and runoff coefficient (C)
Hard surface — ≈61,000 gal/yr total Permeable surface — ≈68,000 gal/yr total

Source: areas from the 1996 site plan, the 2016 3DEP/aerial, and the Lesson 4 zone map; rainfall from the Lesson 1 Climate Survey; runoff coefficients per the Rational Method table (ASCE Manual 37 / WPCF Manual 9) and the Texas Manual on Rainwater Harvesting. Full calc: lesson-05-water/work/rainwater-harvesting-analysis.md.

Site Water Balance

Where an average year's rain goes on the 0.43-acre lot. About three-quarters soaks in or evaporates; the other quarter — ≈129,000 gal — runs off, and today essentially all of it leaves to the Freestone Avenue storm drains.

Today: ~100% of that 129,000 gal/yr of runoff exits to the Freestone Avenue storm drains — the site keeps almost none of it.
Design goal: redirect the runoff into on-site infiltration (extend the NW drip-line swale, add an SE-corner swale / rain garden, a driveway-edge strip) and build soil sponge across the lawn, plus ≈4,400 gal/yr of active harvest from the coop + shed roofs into Zone-3 barrels. No large cistern is warranted.

Source: lesson-05-water/work/rainwater-harvesting-analysis.md — gross rain = 18,730 ft² × 3.625 ft × 7.48; runoff by surface from the Rational Method coefficient table; infiltration + ET taken as the balance.

Elevation Cross-Sections

Ground profiles through the lot, from the USGS 3DEP 1-meter DEM (NAVD88 feet). Vertical scale is exaggerated to make the slope readable. Two cuts: along the lot (street → back) and across it (west ridge → east low).

Section A — along the lot, Freestone Ave (S) → back (N)
~9× vertical exaggeration · the lot rises ~6 ft over ~550 ft ≈ 1% — imperceptible on the ground; the street end is the low end
Section B — across the lot at mid-length, west → east
~5× vertical exaggeration · a ridge crest ~240 ft west (119 ft) is the drainage divide; ground falls east past the lot to a ~90 ft low

Source: USGS 3DEP 1-m DEM sampled Aug 2026 (National Map ImageServer); cross-checked against USGS EPQS. Full transects: lesson-05-water/work/watersheds-water-flow.md.

Site Water-Flow Schematic

Plan view of how water moves across the lot — from the 3DEP 1-meter DEM and the Lesson 4 zone map. A drafting guide for the Figma Site Water Flow Map (template p. 61) and Catchment Area Map (p. 59); trace it over the real base map.

Read: the ridge ~240 ft west is the divide — water arrives from the west / upslope side, crosses east-southeast + south, and exits at the SE corner + frontage to the Freestone Ave storm drains (≈100% today). The existing NW swale ⑤ holds roof water back toward the pool; a new SE-corner swale / rain garden ⑥ would sit in the outlet and catch the lot's whole throughput.

Source: lesson-05-water/work/watersheds-water-flow.md + rainwater-harvesting-analysis.md. Lot width exaggerated ~4× for legibility; contour positions approximate (2-ft interval, NAVD88).

Design-Storm Frequency

24-hour rainfall depth by return period, NOAA Atlas 14 point estimate for the site. The 2-year storm sizes swales and channels; the 100-year storm sizes overflow routing. Regional context: the 1955 state record and the 2024 south-western CT flood.

2-yr 24-hr 3.32 in 10-yr 5.17 in 100-yr 8.09 in CT record 12.77 in (1955)
The 100-year 24-hour storm = 8.09 in. That drops ≈94,000 gal on the 0.43-acre lot and ≈11,400 gal off its ~2,500 ft² of roof and pavement in a single day — the sizing case for every capture feature's overflow path. The Aug 2024 flood (local totals 10–12 in in ~12 hr) shows the tail is not hypothetical.

Source: NOAA Atlas 14 Vol. 10 PFDS, point 41.573, −72.634 (partial-duration series). 1955 record: NWS State Climate Extremes Committee. 2024 event: NWS NY / CT Public.

Macro Watershed

The site drains to the Connecticut River watershed — New England's largest river system — through a nested set of hydrologic units. Whole watershed to parcel is about 26 million : 1.

Nested hydrologic units containing the parcel
drainage area · bar length is log-scaled · USGS Watershed Boundary Dataset
Location within the watershed
Lower Connecticut River valley · east bank, opposite Middletown · ~30 river miles above Long Island Sound
For the template's "Macro Watershed" field: name = Connecticut River watershed, size ≈ 11,260 sq mi (7.2 million acres), four states + Québec headwaters. A tighter alternative for the map: HUC8 Outlet Connecticut River, ≈1,085 sq mi.

Source: USGS WBD point query at 41.573, −72.634; extent via Connecticut River Conservancy / American Rivers. Detail: lesson-05-water/work/watersheds-water-flow.md.

Household Water Use by Season

Metered use per billing period, from four consecutive Town of Portland bills with an unbroken meter trail Sep 2024 – Jun 2026. Bar width = days in the period; bar height = gallons per day. Two adults, no in-ground irrigation.

Annual ≈46,000 gal/yr Average ≈125 gal/day Winter baseline ≈109 gal/day Spring peak 160 gal/day
winter spring summer fall outdoor / growing-season use (above baseline)
The growing-season excess is outdoor use — and it's the size of the harvest prize. Use sits at a ~109 gal/day indoor baseline all winter, then climbs to 133–160 gal/day from spring through summer. That ≈5,000–8,000 gal/yr difference — hose watering, bed prep, pool top-off — is almost exactly the ≈4,400 gal/yr that coop + shed roof barrels could harvest into Zone 3. Because Portland bills sewer on the same metered volume, offsetting it trims both lines of the bill (~$0.017/gal).

Source: Town of Portland Water & Sewer Departments, bills dated 01/15/2025, 07/17/2025, 10/17/2025, 07/17/2026 (service periods 09/24/2024–06/16/2026). Meter readings in cubic feet × 7.48 = gallons. Two periods span an un-imaged bill but the prior/current meter reads chain continuously. Scans in lesson-05-water/assets/.