A Review of Landscape Water Requirements Using a Multicomponent Landscape Coefficient

Water requirements of landscapes are highly variable due to the heterogeneous natures of landscapes, vegetation types, influence of buildings, and nutrient and water management. Objectives for water management of landscapes are for general appearance and health rather than for maximum biomass production. A multi-component method developed for the Irrigation Association (IA) and extended from the California WUCOLS procedure is demonstrated in which the landscape coefficient (KL, equivalent to a crop coefficient) is broken down into four components: vegetation type, vegetation density, microclimate, and managed stress. Each of these components can be estimated using readily made descriptions of a landscaped area and management objectives. One form of the KL equation is used to determine target KL that incorporates a target amount of soil water stress to support water conservation and to support water planning studies. A second form of the KL equation can be used to estimate the actual KL occurring under actual water management. The second form is used in studies of water balances and actual water conservation. The general decoupled equation is further expanded to optionally incorporate impacts of evaporation from exposed soil to assess impacts of irrigation frequency on total water consumption. The mathematics for the approach can be incorporated into software applications and smart irrigation controllers to produce improved water consumption estimates for landscape water requirements for use in irrigation scheduling, water requirement planning, and water depletion studies. The simplified procedure for estimating landscape water requirements in ASABE Standard S623 that is complementary to the IA procedure is discussed and compared. Both methods use a vegetation type and density system as the basis for efficiently estimating scientifically accurate landscape water requirements

A Tree-Ring Based Reconstruction of Logan River Streamflow, Northern Utah

We created six new tree‐ring chronologies in northern Utah, which were used with preexisting chronologies from Utah and western Wyoming to reconstruct mean annual flow for the Logan River, the largest tributary of the regionally important Bear River. Two reconstruction models were developed, a “Local” model that incorporated two Rocky Mountain juniper chronologies located within the basin, and a “Regional” model that also included limber pine and pinyon pine chronologies from a larger area. The Local model explained 48.2% of the variability in the instrumental record and the juniper chronologies better captured streamflow variability than Douglas‐fir collected within the Logan basin. Incorporating chronologies from the northern and southern margins of the transition zone of the western precipitation dipole increased the skill of the Regional model (r 2 = 0.581). We suggest the increased Regional model skill indicates that both nodes of the western precipitation dipole influence northern Utah climate. The importance of Rocky Mountain juniper in both reconstructions of streamflow for this region suggests that future work should target these trees where more traditionally desirable species are not present. The reconstructions provide the first extended record of streamflow in northern Utah. Preinstrumental streamflows (1605–1921) exhibited considerable variability when compared to the instrumental period (1922–2005). Our findings confirm that the inherent uncertainty in contemporary water management and planning in the region is due to hydroclimatic variability that has persisted for at least the last four centuries

A millennium-length reconstruction of Bear River stream flow, Utah

The Bear River contributes more water to the eastern Great Basin than any other river system. It is also the most significant source of water for the burgeoning Wasatch Front metropolitan area in northern Utah. Despite its importance for water resources for the region’s agricultural, urban, and wildlife needs, our understanding of the variability of Bear River’s stream flow derives entirely from the short instrumental record (1943–2010). Here we present a 1200-year calibrated and verified tree-ring reconstruction of stream flow for the Bear River that explains 67% of the variance of the instrumental record over the period from 1943 to 2010. Furthermore, we developed this reconstruction from a species that is not typically used for dendroclimatology, Utah juniper (Juniperus osteosperma). We identify highly significant periodicity in our reconstruction at quasi-decadal (7–8 year), multi-decadal (30 year), and centennial (>50 years) scales. The latter half of the 20th century was found to be the 2nd wettest (∼40-year) period of the past 1200 years, while the first half of the 20th century marked the 4th driest period. The most severe period of reduced stream flow occurred during the Medieval Warm Period (ca. mid-1200s CE) and persisted for ∼70 years. Upper-level circulation anomalies suggest that atmospheric teleconnections originating in the western tropical Pacific are responsible for the delivery of precipitation to the Bear River watershed during the October–December (OND) season of the previous year. The Bear River flow was compared to recent reconstructions of the other tributaries to the Great Salt Lake (GSL) and the GSL level. Implications for water management could be drawn from the observation that the latter half of the 20th century was the 2nd wettest in 1200 years, and that management for future water supply should take into account the stream flow variability over the past millennium

A tree-ring based reconstruction of Logan River streamflow in northern Utah

[1] We created six new tree-ring chronologies in northern Utah, which were used with preexisting chronologies from Utah and western Wyoming to reconstruct mean annual flow for the Logan River, the largest tributary of the regionally important Bear River. Two reconstruction models were developed, a “Local” model that incorporated two Rocky Mountain juniper chronologies located within the basin, and a “Regional” model that also included limber pine and pinyon pine chronologies from a larger area. The Local model explained 48.2% of the variability in the instrumental record and the juniper chronologies better captured streamflow variability than Douglas-fir collected within the Logan basin. Incorporating chronologies from the northern and southern margins of the transition zone of the western precipitation dipole increased the skill of the Regional model (r2 = 0.581). We suggest the increased Regional model skill indicates that both nodes of the western precipitation dipole influence northern Utah climate. The importance of Rocky Mountain juniper in both reconstructions of streamflow for this region suggests that future work should target these trees where more traditionally desirable species are not present. The reconstructions provide the first extended record of streamflow in northern Utah. Preinstrumental streamflows (1605–1921) exhibited considerable variability when compared to the instrumental period (1922–2005). Our findings confirm that the inherent uncertainty in contemporary water management and planning in the region is due to hydroclimatic variability that has persisted for at least the last four centuries

Effects of two contrasting canopy manipulations on growth and water use of London plane (Platanus x acerifolia) trees

Aims: Two contrasting canopy manipulations were compared to unpruned controls on London plane trees, to determine the effects on canopy regrowth, soil and leaf water relations. Methods: ‘Canopy reduction’, was achieved by removing the outer 30 % length of all major branches and ‘canopy thinning’, by removing 30 % of lateral branches arising from major branches. Results: Total canopy leaf areas recovered within two and three years of pruning for the canopy-thinned and reduced trees respectively. Canopy reduction increased mean leaf size, nitrogen concentration, canopy leaf area density and conserved soil moisture for up to 3 years, whereas canopy thinning had no effects. Another experiment compared more severe canopy reduction to unpruned trees. This produced a similar growth response to the previous experiment, but soil moisture was conserved nearer to the trunk. Analysis of 13C and 18O signals along with leaf water relations and soil moisture data suggested that lower boundary layer conductance within the canopy-reduced trees restricted tree water use, whereas for the canopy-thinned trees the opposite occurred. Conclusions: Only canopy reduction conserved soil moisture and this was due to a combination of reduced total canopy leaf area and structural changes in canopy architecture

Establishment of six tree species on deep-tilled minesoil during reclamation

Compaction of replaced soil during reclamation of surface-mined land can limit trees. Growth, survival, and water relations of bare-root seedlings of six tree species were followed on deep-tilled and untilled minesoil for 2 years after planting. Trees were planted in rows deep-tilled to 0.7 m and in untilled soil; mowing and herbicides controlled competing vegetation. Leaf area, shoot elongation, and diameter increment were measured in both years, and predawn and midday water potential, and midday stomatal conductance, were measured in the second year. Survival was 16–98% after the first season, varying more among species than between tillage treatments. Rainfall was 50% less in the second season, resulting in a progressive decline in predawn water potential in all treatments and a decrease in survival for several species on untilled soil. Similarly, trees on deep-tilled soil grew slightly more than those on untilled soil in the second season. Tillage effects on survival and growth were not consistently detectable between years, however, and 3 years after planting there were no further changes in survival. Differences in survival and growth among species were large. Survival of black locust was approximately double that of any other species, and its growth was several orders of magnitude greater than that of other species, whereas all of the tulip poplars died by the end of the second season. Over 2 years it appeared that most species had not grown enough either to exploit fully the deep-tilled soil or to be impeded on the untilled soil such that differences in establishment could be detected. The full impact of deep tillage on reclamation with trees must be assessed, however, by following growth and survival over a longer time period