Garden Irrigation with Harvested Rainwater in Wisconsin

Using harvested rainwater for garden irrigation in Wisconsin is a practical way to reduce your water bill and conserve municipal supplies. With 33.2 inches of average annual rainfall, a 1,500-square-foot asphalt shingle roof in Wisconsin can collect approximately 24,221 gal per year. garden irrigation requires roughly 50 gallons per day, during the growing season (April through October). With this setup, rainwater can meet approximately 100.0% of your garden irrigation needs, saving an estimated $53.50 per year.

Annual Harvest 24,221 gal 1,500 sq ft roof
Annual Demand 10,700 gal garden irrigation
Demand Met 100.0% of garden irrigation
Rec. Tank 2,500 gal storage capacity

Monthly Supply vs. Demand for Garden Irrigation in Wisconsin

The table below shows how your monthly rainwater harvest compares to garden irrigation demand throughout the year. Green values indicate months where your harvest exceeds demand (surplus water for tank storage), while red values show months where you will draw down your stored reserves. Since garden irrigation is a seasonal activity, demand is zero from November through March, allowing you to build up tank reserves during the off-season.

Month Harvest (gal) Demand (gal) Balance
January 897 0 +897
February 897 0 +897
March 1,495 0 +1,495
April 2,243 1,500 +743
May 2,691 1,550 +1,141
June 2,990 1,500 +1,490
July 2,841 1,550 +1,291
August 2,691 1,550 +1,141
September 2,542 1,500 +1,042
October 1,944 1,550 +394
November 1,794 0 +1,794
December 1,196 0 +1,196

Harvest by Roof Size for Garden Irrigation

A larger roof collection area directly increases your harvest and the percentage of garden irrigation demand you can meet with rainwater. The table below shows how different roof sizes perform in Wisconsin for garden irrigation.

Roof Area Annual Harvest Demand Met Rec. Tank Savings/Year
1,000 sq ft 16,148 gal 100.0% 1,500 gal $53.50
1,500 sq ft 24,221 gal 100.0% 2,500 gal $53.50
2,000 sq ft 32,295 gal 100.0% 2,500 gal $53.50
2,500 sq ft 40,371 gal 100.0% 5,000 gal $53.50

Setting Up Rainwater Harvesting for Garden Irrigation in Wisconsin

Garden irrigation is the simplest and most popular application of harvested rainwater in Wisconsin. Start with a single rain barrel connected to a downspout near your garden. For larger gardens, upgrade to a 500-1,000 gallon tank with a drip irrigation system. Rainwater's natural softness and absence of chlorine make it preferred by plants — many gardeners report healthier growth and better yields when switching from municipal water to rainwater. In Wisconsin, focus on capturing spring rains to build reserves for the peak growing season. A timer-controlled drip system connected to your tank ensures consistent watering while minimizing waste.

Metal Roof Upgrade: Garden Irrigation in Wisconsin

Upgrading to a metal roof increases your collection efficiency from 80% (asphalt shingle) to 95%, boosting your annual harvest to 28,763 gal from a 1,500-square-foot roof. This increases your garden irrigation demand coverage to 100.0% and raises annual savings to $53.50. Metal roofs also last 40-70 years compared to 20-30 years for asphalt shingle, and their smooth surface sheds debris more effectively, reducing maintenance on your collection system and improving water quality.

Other Uses for Rainwater in Wisconsin

Explore how harvested rainwater can serve other needs in Wisconsin:

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