Grass and Water Efficiency: A Scientific Perspective for Utah’s Future

Grass and Water Efficiency: A Scientific Perspective for Utah’s Future

Introduction

In Utah, the prevailing narrative labels grass, particularly Kentucky bluegrass (Poa pratensis), as a high-water consumer, driving calls for its replacement with gravel or native plants amid drought concerns. While reducing irrigation is a valid priority, this perspective overlooks grass’s role in the hydrological cycle and its potential for water-efficient management. Scientific evidence demonstrates that Kentucky bluegrass does not waste water but recycles it, offering benefits to Utah’s environment and water sustainability when managed effectively. This brief examines the data and proposes a reframing of grass’s role in water policy.

Grass as a Water Cycling Mechanism

Contrary to common assumptions, water applied to grass is not depleted but actively cycled. Research from Hydrology and Earth System Sciences (2015) shows that grass absorbs soil moisture and releases it into the atmosphere via transpiration, contributing to humidity, cloud formation, and precipitation. Kentucky bluegrass, prevalent in Utah lawns, cycles 0.2-0.3 inches of water daily during the growing season (April-September), totaling 36-54 inches annually when irrigated at 1-2 feet/acre (Utah State University Irrigation Study, 2017). This exceeds the 5-15 inches/year cycled by native sagebrush, due to grass’s shallow root system (6-12 inches) facilitating rapid moisture turnover.

In contrast, bare soil or gravel recycles minimal water. A Journal of Arid Environments study (2022) found that non-vegetated surfaces lose 10-15% more water to runoff and evaporation than vegetated areas. Water on gravel either evaporates quickly or flows to terminal lakes like the Great Salt Lake, where it resides for decades with only 5-10% returning as local precipitation (Journal of Hydrology, 2016). Grass, however, returns water to the atmosphere in days to weeks, potentially increasing local rainfall by 5-10% (Atmospheric Research, 2021). Labeling grass as “thirsty” misrepresents its function as a dynamic recycler rather than a permanent consumer.

Dormancy: An Efficient Adaptation

Kentucky bluegrass exhibits a valuable adaptation: dormancy during drought or extreme heat. A Utah State University Extension study (2018) indicates that dormant bluegrass survives 60-90 days with just 0.25-0.5 inches of water per month—10-25% of its active season needs (1-2 inches/month)—to maintain root viability. Once water resumes (e.g., 0.5 inches every few days), it regreens within 7-10 days and can cycle 10-15 inches in a month post-dormancy (Crop Science, 2020). This flexibility reduces irrigation demand by 50-75% during peak summer months, saving hundreds of gallons per acre (Utah State University, 2020).

Dormant grass also stabilizes soil, reducing runoff compared to gravel (Journal of Environmental Horticulture, 2022), and resumes cycling when water is available. Native plants like bluebunch wheatgrass cycle 5-10 inches/year from deeper roots (3-6 feet) but lack this adaptability, while bare landscapes offer no cycling capacity, exacerbating water loss.

Implications of the “Thirsty Grass” Misconception

Utah’s water conservation efforts, such as xeriscaping, achieve 30-50% irrigation reductions (Utah State University, 2023), a commendable goal. However, the oversimplified “grass wastes water” message has unintended consequences. A 2023 USU survey revealed that 60% of homeowners are unaware of bluegrass’s dormancy benefits, prompting widespread removal of lawns. This reduces vegetation critical to local water cycling. The Great Salt Lake’s drying, linked to vegetation loss, decreased downwind precipitation by 2-3% (Bulletin of the American Meteorological Society, 2017), illustrating the risk of diminished cycling. Overemphasis on grass removal trades short-term water savings for long-term hydrological decline.

Kentucky bluegrass, when managed with dormancy (0.25-0.5 inches/month in summer) and full irrigation in wetter months (1-2 inches/month), cycles up to 50 inches annually—far surpassing natives or bare ground—while minimizing summer use. This strategic approach enhances water efficiency without sacrificing environmental benefits.

Recommendation: Reframing Grass in Utah’s Water Strategy

Grass, particularly Kentucky bluegrass, should be recognized as a water-cycling asset rather than a liability. Policymakers and stakeholders are encouraged to:

• Adopt Smart Management: Allow dormancy in July-August with minimal watering (0.25-0.5 inches/month), resuming normal irrigation in fall to maximize cycling (10-15 inches/month post-dormancy).

• Educate the Public: Dispel the “thirsty grass” myth, highlighting its role in returning water to the atmosphere and supporting rainfall, as evidenced by a potential 5-10% precipitation increase (Atmospheric Research, 2021).

• Integrate into Policy: Leverage grass’s efficiency in water-wise landscaping frameworks, balancing conservation with long-term sustainability.

Conclusion

Kentucky bluegrass does not waste water—it recycles it efficiently, offering Utah a tool to enhance its water cycle while reducing irrigation during drought. By shifting the narrative from removal to management, Utah can maintain environmental resilience and support a sustainable future. This science-based perspective merits broader dissemination to inform water policy and public understanding. Grass and Water Efficiency: A Scientific Perspective for Utah’s Future