Laurel Saito

Special Section on Climate Change and Water Resources: Climate Nonstationarity and Water Resources Management

Over the past three decades, hydrologists and water resources specialists have been concerned with the issue of nonstationarity arising from several factors. First is the effect of human intervention on the landscape that may cause changes in the precipitation–runoff relationships at various temporal and spatial scales. Second is the occurrence of natural events such as volcanic explosions or forest fires that may cause changes in the composition of the air, the soil surface, and geomorphology. Third is the low-frequency component of oceanic–atmospheric phenomena that may have significant effects on the variability of hydrological processes such as annual runoff, peak flows, and droughts. Fourth is global warming, which may cause changes to oceanic and atmospheric processes, thereby affecting the hydrological cycle at various temporal and spatial scales. There has been a significant amount of literature on the subject and thousands of research and project articles and books published in recent decades. Examples of human intrusion on the landscape are the changes in land use resulting from agricultural developments in semiarid and arid lands (e.g., Pielke et al. 2007, 2011), changes caused by large-scale deforestation (e.g., Gash and Nobre 1997), changes resulting from open-pit mining operations (e.g., Salas et al. 2008), and changes from increasing urbanization in watersheds (e.g., Konrad and Booth 2002, Villarini et al. 2009). These intrusions change hydrologic response characteristics such as the magnitude and timing of floods. In many situations, current systems and management practices will be ill equipped to cope with such changes unless adjustments are made. Large-scale landscape changes such as deforestation in the tropical regions can potentially alter atmospheric circulation patterns, and consequently affect global weather and climate (e.g., Lee et al. 2008, 2009). Major natural events, such as the volcanic explosion of Mount St. Helens in 1980 or the El Chichon volcanic explosion of 1982 induce a shock to the climate system in the form of global cooling that continues for several years. These events can also affect global circulation. Low-frequency climate drivers of the oceanic– atmospheric system such as the El Nino/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and Arctic Oscillation (AO) modulate global climate at interannual and multidecadal time scales. These drivers are the main sources of nonstationarity in global climate and hydrology. Large numbers of papers documenting the effect of these drivers on global hydroclimatology continue to emerge (e.g., Dilley and Heyman 1995; Mantua et al. 1997; Enfield et al. 2001; Akintug and Rasmussen 2005; Hamlet et al. 2005). In addition to climate variability and change due to the previously mentioned factors, anthropogenic warming of the oceans and atmosphere because of increased greenhouse gas concentrations and the ensuing changes to the hydrologic cycle are topics of serious pursuit. The international scientific community is making strides in understanding the potential warming and its effects on all aspects of climate variability [Intergovernmental Panel on Climate Change (IPCC) 2007], but the impacts on the hydrologic cycle remain debatable and inconclusive (e.g., Cohn and Lins 2005; Legates et al. 2005; Hirsch and Ryberg 2011). Based on analyses of the global mean CO2 (GMCO2) and annual flood records in the United States, no strong statistical evidence for flood magnitudes increasing with GMCO2 increases were found (Hirsch and Ryberg 2011). Although general circulation models have had success in the attribution of warming global temperatures to anthropogenic causes, their credibility and utility in reproducing variables that are relevant to hydrology and water resources applications is less clear. For example, the IPCC Report for Latin America acknowledges that “the current GCMs do not produce projections of changes in the hydrological cycle at regional scales with confidence. In particular the uncertainty of projections of precipitation remain high : : :That is a great limiting factor to the practical use of such projections for guiding active adaptation or mitigation policies” (Magrin et al. 2007; Boulanger et al. 2007). A variety of methods exist that address the concern of nonstationarity in hydrological processes and the topic remains an active research area. For example, in watersheds in which increasing urbanization has been documented causing significant effects in the flood response and magnitude, watershed modeling has been utilized to estimate the possible changes in the flood frequency and magnitude. Frequency analysis methods also have been applied when the parameters (or the moments such as the mean and variance) of a given model (e.g., the Gumbel model) may vary with time (e.g., Strupczewski et al. 2001; Clarke 2002). In addition, the role that low-frequency components of the oceanic– atmospheric system (represented, for example, by large-scale oscillations such as ENSO, PDO, and AMO) have on extreme events such as floods has been recognized. These large-scale forcing factors have been shown to exert in-phase and out-of-phase oscillations in the magnitude of floods, mean flows, and droughts

A watershed modeling approach to streamflow reconstruction from tree-ring records

Insight into long-term changes of streamflow is critical for addressing implications of global warming for sustainable water management. To date, dendrohydrologists have employed sophisticated regression techniques to extend runoff records, but this empirical approach cannot directly test the influence of watershed factors that alter streamflow independently of climate. We designed a mechanistic watershed model to calculate streamflows at annual timescales using as few inputs as possible. The model was calibrated for upper reaches of the Walker River, which straddles the boundary between the Sierra Nevada of California and the Great Basin of Nevada. Even though the model incorporated simplified relationships between precipitation and other components of the hydrologic cycle, it predicted water year streamflows with correlations of 0.87 when appropriate precipitation values were used.

Toward a Sustainable Water Future: Visions for 2050

This collection of essays challenges readers to consider how society can manage natural and cultural resources to benefit present and future generations. It will be of particular interest to students, educators and practitioners in water resource engineering, as well as planners, environmental managers, and government officials at all levels.

Ecosystem and Social Construction: an Interdisciplinary Case Study of the Shurkul Lake Landscape in Khorezm, Uzbekistan.

Transformation of the Khorezm region of Uzbekistan from forested to agricultural landscapes resulted in the formation of hundreds of lakes, the dynamics of which are largely controlled by inputs from irrigation runoff waters. The importance of the ecological and socio-cultural dimensions of one of these lakes, Shurkul, is discussed in order to understand the connection between humans and their environment. Landscape is used as a boundary concept, and we combine quantitative methods of the natural sciences with qualitative methods of the social sciences to assess these dimensions of the lake landscape. In the ecological dimension, Shurkul performs a wide range of ecosystem services from wildlife habitat and foodweb support to the provision of fish, fodder, building material and grazing ground. In the socio-cultural dimension, the lake is part of local ecological knowledge, functions as a prestige object and recreational site, and is rooted in religious beliefs of the population as a symbol of Gods benevolence. The Shurkul landscape may thus create a feeling of environmental connectedness and the desire to act in favor of the natural environment, which could be made use of in environmental education programs.

Instrumenting Wildlife Water Developments to Collect Hydrometeorological Data in Remote Western U.S. Catchments

In the arid western United States, wildlife water developments, or ‘‘guzzlers,’’ are important water sources for wildlife, and consist of impermeable roof structures designedto intercept precipitation and small tanks for storing water. Guzzlers are typically installed in remote mid- to high-elevation basins, where precipitation data are often scarce. In this study, small-game guzzlers were examined for feasibility as potential sites for improving estimates of climatic parameters in remote Nevada catchments. Instruments measuring liquid precipitation and water level were installed at two guzzler field sites. Although one field site was vandalized during the study, field results indicated that water levels in the tank measured by Hobo pressure transducers corresponded well with precipitation events measured by the Texas Electronics tipping-bucket rain gauge, and that measured data were similar to Parameter‐Elevation Regressions on Independent Slopes Model (PRISM) estimates. Minimum temperatures from the guzzler sites were similar to PRISM; however, maximum temperatures were a few degrees higher, possibly because temperature sensors were unshielded. With over 1600 guzzlers in Nevada and thousands more throughout the western United States, this study initiates exploration of the feasibility of augmenting individual guzzler sites to enhance climatic monitoring at a relatively low cost to improve the quality and density of climate observations, benefitting hydrologists, climatologists, and wildlife managers.

Road to 2050: Visions for a More Sustainable Future

There are two ways to embrace the future: we can passively let the future happen and react to it, or alternatively we can actively shape the future by taking specific steps that will beneficially effect the state of the world and the resources available to those living in the future. To take a more active approach toward shaping our future, we need to have a vision of what kind of a future we want. Approximately two years ago, we encouraged some 50 experienced professionals in environmental and water resources engineering, ecology, and economics, employed by consulting firms, academia, governmental, and nongovernmental agencies, to create such visions on the basis of optimistic expectations. These visions are now in a book (Grayman et al. 2012) that attempts to identify just what we can and should do over the next few decades to shape the future that we would like to see and inhabit in the year 2050. The book’s goal is to motivate some thinking about how we as a society want to achieve a more perfect world. It considers sustainability and how we develop and manage our natural and cultural resources to benefit both our and future generations. We guess what future generations would tell us about how we should develop today and manage our water resources and environment, so that they, our children or grandchildren, some 40 years later, will be better able to meet their needs, achieve their goals, and improve the quality of their lives. Our visions fit into three broad categories: Planning and Policy; Education; and Science and Technology. Pervasive themes in the collection of visions for 2050 include (1) managing water resources variability (floods and droughts) considering nonstationarity; (2) providing adequate and reliable supplies of clean water, food, energy, and sanitation to expanding populations, especially in urban areas; (3) developing new options for addressing water and environmental management issues provided by rapidly advancing technology; (4) changing our educational system considering technological and economic factors; and (5) planning and managing water and environmental resources with adaptable, robust, and integrated approaches. It is relatively easy to create alternative visions of an ideal 2050 but much harder to get society to reach a consensus vision and to meet the challenges of achieving that vision. We often focus on satisfying short-run goals to the exclusion of longer-term ones. An example of this type of challenge from the book concerns the aging and deteriorating water resources infrastructure in the United States (Grayman et al. 2012): In the US, aging, broken or under-designed wastewater collection and treatment systems discharge billions of liters of untreated wastewater into surface waters each year. The US Environmental Protection Agency estimates that

Quantifying foodweb interactions with simultaneous linear equations: stable isotope models of the Truckee River, USA

390 billion (today’s dollars) will be needed over the next 20 years to update or replace existing systems and build new ones to meet increasing demands (ASCE 2010). Just where is this amount of money going to come from? How will the necessary political support be created and sustained over the next 40 years? Do we need to wait until the failure rate and associated inconveniences exceed some threshold before people say enough? Perhaps we need to market this gaping long-standing need in infrastructure (and not just water-related infrastructure) as a “war” on infrastructure decay ... Can we develop and implement a sewerless technology? Can we eliminate the use of sewers and the use of treated high quality water to transport wastewater from our toilets to wastewater treatment plants? Can wastewaters from urban apartments and office buildings be “treated” on site, eliminating, in a cost-effective way, the need for sewers in urban areas? Can we think of cities that are green with vegetation that effectively and substantially reduces the need for stormwater sewers and instead promotes runoff infiltration into the ground? As a vision for 2050, why not? Indeed steps in this direction are already being taken in various cities of the world.

A K-Nearest neighbor based stochastic multisite flow and stream temperature generation technique

Abstract Aquatic foodweb models for 2 seasons (relatively high- [March] and low-flow [August] conditions) were constructed for 4 reaches on the Truckee River using δ13C and δ15N data from periphyton, macroinvertebrate, and fish samples collected in 2003 and 2004. The models were constructed with isotope values that included measured periphyton signatures and calculated mean isotope values for detritus and seston as basal food sources of each food web. The pseudo-optimization function in Excels Solver module was used to minimize the sum of squared error between predicted and observed stable-isotope values while simultaneously solving for diet proportions for all foodweb consumers and estimating δ13C and δ15N trophic enrichment factors. This approach used an underdetermined set of simultaneous linear equations and was tested by running the pseudo-optimization procedure for 500 randomly selected sets of initial conditions. Estimated diet proportions had average standard deviations (SDs) of 0.03 to 0.04‰, and SDs of trophic enrichment factors ranged from <0.005 to 0.05‰ based on the results of the 500 runs, indicating that the modeling approach was very robust. However, sensitivity analysis of calculated detritus and seston δ13C and δ15N values indicated that the robustness of the approach is dependent on having accurate measures of all observed foodweb-component δ13C and δ15N values. Model results from the 500 runs using the mean isotope values for detritus and seston indicated that upstream food webs were the simplest, with fewer feeding groups and trophic interactions (e.g., 21 interactions for 10 feeding groups), whereas food webs for the reach downstream of the Reno–Sparks metropolitan area were the most complex (e.g., 58 interactions for 16 feeding groups). Nonnative crayfish were important omnivores in each reach and drew energy from multiple sources, but appeared to be energetic dead ends because they generally were not consumed. Predatory macroinvertebrate diets varied along the river and affected estimated trophic positions of fish that consumed them. Differences in complexity and composition of the food webs appeared to be related to season, but could also have been caused by interactions with nonnative species, especially invasive crayfish.

Modeling Contaminant Spills in the Truckee River in the Western United States

Hydrologic and climatic uncertainty is increasing in the western United States, and with it the need for models capable of capturing this uncertainty beyond what is seen in the historical record for planning and management purposes. This is especially important for managing water resources on Lake Shasta under water supply and stream temperature constraints. We develop K-nearest neighbor based stochastic simulation methods for daily streamflow and attendant stream temperature at five streams that drain into Lake Shasta. The methods can also generate scenarios conditioned on the larger climate e.g., extreme wet or extreme dry. The ability of the methods to capture the historical variability of flow and temperature for Lake Shasta is demonstrated. Although, we developed and demonstrated this technique for Lake Shasta, they can be readily applied to any water resource systems. A K-Nearest Neighbor bootstrap technique for stochastic simulation of daily flow and stream temperature at multiple sitesSimulation of daily streamflow and temperature conditioned on flow characteristics such as, extreme wet, extreme dry etc.The method can also be applied for ensemble seasonal forecasting based on seasonal climate forecast.

Improving estimates of oil pollution to the sea from land-based sources.

Originating at Lake Tahoe, the Truckee River provides 85% of drinking water for the Reno/Sparks metropolitan area. Major highways and a railroad run adjacent to the river, which increases risk of a contaminant spill into the river that could have detrimental effects on drinking water supplies. A one-dimensional solute transport model (OTIS) was applied to the Truckee River. Data from dye studies on the river were used to determine a relationship to estimate dispersion coefficients for the Truckee River and calibrate the model. Two sizes of hypothetical contaminant spills from 9 locations under 13 flow scenarios were simulated. Travel times to the first water intake for a train spill of 130,000 L ranged from 3 to 46 h and maximum simulated concentrations of a conservative water soluble contaminant at the intake ranged from 340 to 4,800 mg=L. Model output was influenced by uncertainties in the equation for longitudinal dispersion, so model runs were executed with estimated dispersion values that were a factor of 1.5 greater and less than the equation-estimated value of dispersion. DOI: 10.1061/(ASCE)WR.1943-5452.0000338.