BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

5.3.2.2 IRRIGATIONProper irrigation helps establish vegetation and will also maintain plants notadapted to the Lake Tahoe Region’s climate. Vegetation establishment mayrequire more frequent and/or intensive watering than maintaining healthymature plants with deep, strong roots.Water application methods including drip and bubbler systems. Drip irrigationis a method of irrigation using the slow application of water under lowpressure through tube openings or attached devices just above, at or below thesoil surface.A bubbler is a water emission device that tends to bubble water directly ontothe ground or that throws water a short distance. It is a more directed ortargeted irrigation method than traditional sprinkler nozzles, enabling water toget to plants with increased efficiency. It is a suitable system for smalllandscaped areas.Micro-irrigation systems include drip or trickle irrigation as well as microsprayand other new devices operating at low pressures. Water is appliedfrequently just above, on or below the surface of the soil at low flow rates withthe goal of placing a quantity of water in the root zone that nearlyapproximates the consumptive use of the plant. These systems conserve waterbut also support healthy plants by preventing overwatering.Irrigation systems should consider the following four factors:Delivery System and Application Rate - Adjust sprinkler nozzles to avoid watering pavedareas or other spots not intended for watering. Use the right size nozzles – the size of thenozzle should be consistent with the size of the area it wets. Use an efficient irrigationsystem such as a drip irrigation system to avoid excessive leaching and runoff of nutrients.Soils - Different soil types hold different amounts of water. Soils in the Lake Tahoe Regionare mostly loamy sands and coarse sandy loams that can only hold 0.5 inches of water inthe top foot of soil.Root Zones - The roots of typical turf species are mostly confined to the first 12 inchesbelow the surface. Watering beyond the root zone will result in wasted water, and carryany applied fertilizers beyond the reach of roots, in turn resulting in less vigorous plantsdue to nutrient deficiency, increased costs for lawn maintenance and water, and potentiallycreating nutrient laden runoff that pollutes Lake Tahoe.Water Use - Plants require different amounts of water at different times of the year,peaking in July and August. In general, deep (but not excessive) and infrequent wateringproduces healthier and more resilient plant roots than shallow, frequent watering.For the soils typically found in the Lake Tahoe Region, the NRCSrecommends applying ½ inch of water to turf and lawns. To measure this,place a container on the lawn and time how long it takes your sprinkler systemTRPA BMP HandbookCHAPTER 5: Soil and Vegetation Management2012 Page 5-11