Water in the region we design in.

The DFW precipitation average is not misleading — roughly 36 to 38 inches per year is what the thirty-year averaging windows return — but the distribution across the calendar is. Spring and early fall carry the bulk of the rainfall in bimodal peaks, with May as the wettest month in most DFW stations. Summer, by contrast, is a functional drought window: July and August routinely produce under two inches of rain each while daily high temperatures run in the upper 90s, and the combination of low rainfall and high temperature means evapotranspiration demand outruns precipitation supply for roughly 100 to 120 days every year. A planting design that sizes irrigation against average-rainfall assumptions will under-water the garden for a third of the calendar.

Winter is the second surprise. December through February rainfall is lighter than most homeowners expect; much of the moisture that carries Blackland clay through the dormant season is residual from October rains rather than winter precipitation. The consequence is that freeze events often land on a substrate already moderately dry — which is part of what made Winter Storm Uri as hard on residential plantings in February 2021 as it was. Five days of sub-freezing soil temperatures on already-stressed root systems produced a wider range of plant failures than the simple temperature exposure alone would suggest.

Every lot in the Alterra service area drains to the Trinity River, which is a four-forked system wrapping the metro rather than a single channel through it. The West Fork rises in Archer County and runs through downtown Fort Worth; the Clear Fork joins it at Fort Worth; the Elm Fork comes in from Lewisville Lake and defines the western Dallas edge; the East Fork drains Lake Lavon and the Collin County side, running south through Rockwall and joining the main stem below Dallas. The four forks converge near downtown Dallas, and from there the Trinity drains east and south through the Gulf Coastal Plain to Galveston Bay. A design-phase drainage read on any Alterra site is ultimately a Trinity-system read, and the short-path tributaries — White Rock Creek through east Dallas, Turtle Creek through Highland Park, Bachman Creek on the Elm Fork side — carry the finer-scale drainage patterns that individual neighborhood lots actually feed into.

The Trinity system supplies most of the metro's municipal water through surface reservoirs: Lewisville Lake, Lake Ray Hubbard, Lake Lavon, Cedar Creek Reservoir, Richland-Chambers, and others operated by the North Texas Municipal Water District (NTMWD) and the Dallas Water Utilities. Groundwater plays a secondary role through the Trinity Aquifer, which underlies the region but is not the dominant residential-water source. Both systems respond to multi-year drought on the lagged schedule that reservoirs impose — which means that landscape irrigation in a third consecutive drought year is operating under constraints shaped by precipitation two or three years in the past.

July and August in DFW produce pan-evaporation rates that pull significant moisture out of the soil column every day the sun is out. The practical implication on a residential site is that irrigation through the summer demand window is not making up a small shortfall; it is doing roughly half the water work that carries a garden through a typical summer, with rainfall doing the other half in unpredictable bursts. Plant species that cannot cooperate with that ratio fail quietly during the first or second summer. Species selected against it — the natives and carefully-chosen adapted species that compose the working palette — survive on a watering schedule that tapers toward near-zero supplemental demand by year three of establishment.

The 2011 single-year drought established the working benchmark for how hard that demand window can push. That year's cumulative precipitation deficit and record-setting summer temperatures killed significant mature canopy across the DFW metro — losses still visible in neighborhood tree inventories today — and the lesson on the design side was that canopy inventory on any residential lot is fragile in a way the calendar-average rainfall number conceals. A 2022 multi-year deficit, layered on a separate set of lot-by-lot conditions, made a similar point at smaller scale. The right reading of both events is that drought in DFW is the expected condition that a design has to anticipate rather than the exception the design can survive on average terms.

Grading and drainage run first. A Blackland lot with heavy clay in the top foot sheds water slowly; a Cross Timbers lot with sandy loam sheds water fast. Either way, the design has to move water off the house envelope and onto the planted edges that can receive it — terrace pitch, swale placement, and downspout termination points are landscape-design decisions, not contractor field calls. Permeable edges along paved terraces reduce runoff onto turf and feed moisture laterally into adjacent planting beds; this is the detail that distinguishes a terrace drawn with the water cycle in mind from one drawn as a slab-and-stone assembly indifferent to it. See outdoor living for terrace and drainage detailing at the built-line level.

Irrigation follows. Drip-first systems with zone logic tuned to plant water needs — not to area-coverage convenience — are the working standard across the practice. Emitters are sized to the root zone of the species they serve, not to a default flow rate. Overhead spray is reserved for turf areas where the homeowner requires it; drip and bubbler carry everything else. Manifolds are placed in sheltered microclimates with freeze protection specified per the post-Uri spec, and the controller program at handoff carries multi-stage drought response as named programs — a Stage 1, Stage 2, Stage 3 schedule that maps onto each city's drought-contingency ordinance. Read the full specification at the resilience section.

Plant selection follows both. Species that survive a multi-year deficit without supplemental irrigation after establishment are the working palette; species that require supplemental water indefinitely do not belong in a drought-cycle region no matter what register the register-driven design conversation is aiming for. That filter runs in the same direction as the post-Uri freeze filter and the alkaline-clay filter — the palette that passes all three is narrow but entirely workable.

The Texas Commission on Environmental Quality (TCEQ) administers the state's landscape-irrigation licensure framework. Licensed Irrigator (LI) and Irrigation Technician credentials are required to design and install irrigation on Texas residential projects, and the credential carries a continuing-education requirement that keeps practitioners current with evolving water-rule interpretation. Backflow prevention specifications, pressure testing at completion, and audit documentation are licensure-driven — these are not optional best practices but regulated installation elements that a TCEQ-licensed irrigator carries into the work. Alterra's TCEQ LI credentials are on record and available on request.

The North Texas Municipal Water District coordinates drought-contingency across most of the Collin County service area (Plano, Frisco, Prosper, Richardson, Lucas, McKinney), with each member city enforcing a localized version of the district's multi-stage framework. Stage 1, Stage 2, and Stage 3 correspond to reservoir-level thresholds that trigger progressive watering restrictions — day-of-week limits, time-of-day limits, cycle-and-soak rules, and at higher stages, outright prohibitions on certain categories of landscape water use. Dallas operates under its own Dallas Water Utilities framework with similar logic but distinct thresholds. The design-phase discipline at Alterra includes a review of each project city's current contingency stage and its implications for the irrigation spec, so a project permitted during a Stage 2 window is not designed against a schedule that becomes illegal the month after installation.