Andrew F. Colombo

Climate Variability and the Frequency of Extreme Temperature Events for Nine Sites across Canada: Implications for Power Usage

To study the impact of incremental climatic warming on summer extreme temperature event frequency, the historical record of daily maximum June, July, and August temperatures was analyzed for nine sites across Canada. It was found that all of these sites are well modeled by a first-order autoregressive process using three parameters: the mean, variance, and first-order autocorrelation coefficient. For slight changes in the mean or variance there are increases in the frequency of both single days and runs of 2‐5 consecutive days with daily maximum temperatures over a threshold value. For example, for a 38C increase in the mean daily maximum temperature at Toronto, the frequency of a 5-day consecutive run over 308C rose by over a factor of 8 to 7.1%. Sites with less variability are more sensitive to an increase in the mean summer temperature than sites with higher variability. Analysis of simulated series indicates that when two parameter values change simultaneously the change in the frequency of a given event is usually greater than the sum of the individual changes. Output from the Canadian Climate Centre GCMII model for the nine sites for both the current and 2 3 CO2 atmosphere indicate an average increase in the daily maximum temperature of 4.28C. Changes in the standard deviation and autocorrelation were usually less pronounced. For Toronto, a positive correlation (R2 5 0.718) between daily peak power demand and the cube of the current and previous 2 days daily maximum temperature was found. A sensitivity analysis was performed on daily peak power demand by first generating temperature time series and then using the derived regression relationship. Results follow a predictable pattern and indicate that the standard deviation of the peak power series increases proportionally more than the mean for increases in the mean daily maximum temperature. For example, for a 38C increase in mean daily maximum temperature, the increase in mean peak power demand was 7% (1200 MW) while the increase in the standard deviation of peak power demand was 22%. Changes in the autocorrelation of the temperature time series do not lead to significant changes in the mean or standard deviation of daily peak power demand. These results indicate that, while the average peak power demand is not moved drastically, the number of high energy consumption days may increase appreciably due to higher variability, placing stress on the provincial power utility to meet this higher demand.

Stochastic Analysis of Water Hammer and Applications in Reliability-Based Structural Design for Hydro Turbine Penstocks

The randomness of transient events, and the variability of its associated dependencies, ensures that water hammer and surges in a pressurized pipe system are inherently stochastic. To improve reliability-based structural design, a stochastic transient model is developed for water conveyance systems in hydropower plants. The statistical characteristics of key factors in boundary conditions, initial states, and hydraulic system parameters are analyzed on the basis of a large record of observed data from hydro plants in China; the probability distributions of annual maximum water hammer pressures are then simulated by using a Monte Carlo method and verified with an analytical probabilistic model for a simplified pipe system. The key loading characteristics (annual occurrence, sustaining period, and probability distribution) are introduced and discussed. By using an example of penstock structural design, it is shown that the total water hammer pressure should be split into two individual random variable loads—the steady/static pressure and the water hammer pressure rise during transients—and that different partial load factors should be applied to individual loads to reflect specific physical and stochastic features. Particularly, the normative load (usually the unfavorable value at a 95-percentage level) for steady/static hydraulic pressure should be taken from the probability distribution of its maximum values over a pipe’s design life, whereas for the water hammer pressure rise, as the second variable load, the probability distribution of its annual maximum values determines its normative load.

Adaptation, flexibility and project decision-making with climate change uncertainties

Project planning in the future must directly address both climate change and uncertainties about it. This paper presents the use of classical decision criteria, such as maximin and minimax regret, and approaches for adapting to climate change given the uncertainties. Adaptation strategies can help reduce the effects of uncertainties by allowing for adjustments in designs as the future climate evolves, although at a cost for such future flexibility. Adding such options and evaluating them against other design options using the decision criteria can provide valuable information to decision-makers and other stakeholders during project planning. A hypothetical example of a hydroelectric project illustrates the use of these approaches.

Water Resource Management for Iran’s Persepolis Complex

The historical patrimony of any civilization offers numerous vantage points from which to base inquiry into the rich tapestry that weaves its cultural, political, economic, technical, social and natural characteristics. An ancient culture’s interactions with water, and its early attempts at managing it, provide an intriguing lens through which to observe how a society’s growth and development are linked with this precious resource. Early human societies devised straightforward but elegant and innovative-technical solutions for sequestering and allocating the often limited sources of water they knew, redirecting essential quantities from rivers and other surface deposits to both urban and rural areas. In this way, the ancients established the foundation not only for their own economic and cultural development, but also for contemporary water resources engineering. Indeed, water resources management played an important role in all early urban settlements. In Iran, due to frequent drought, thoughtful attention was paid to reliable design. This is particularly evident at the Persepolis complex, the ancient capital of the Achaemenid dynasty. This monument is situated in Fars province in southwest Iran and was built approximately 2,500 years ago by the Mesopotamian civilization. Various water aspects of the Persepolis complex are presented in historical context with commentary on their present condition. Ruins of the runoff system and sewer network of the complex are analyzed to help envisage the original system and how it functioned.