Search

Streamflow in Western North America (WNA) has been experiencing pronounced changes in terms of volume and timing over the past century, primarily driven by natural climate variability and human-induced climate changes. This thesis advances on previous work by revealing the most recent streamflow changes in WNA using a comprehensive suite of classical hydrometric methods along with novel Deep Learning (DL) based approaches for change detection and classifica- tion. More than 500 natural streams were included in the analysis across western Canada and the United States. Trend analyses based on the Mann-Kendall test were conducted on a wide selection of classic hydrometric indicators to represent varying aspects of streamflow over 43 years from 1979 to 2021. A general geograph- ical divide at approximately 46◦N degrees latitude indicates that total streamflow is increasing to the north while declining to the south. Declining late summer flows (July–September) were also widespread across the WNA domain, coinciding with an overall reduction in precipitation. Some changing patterns are regional specific, including: 1) increased winter low flows at high latitudes; 2) earlier spring freshet in Rocky Mountains; 3) increased autumns flows in coastal Pacific North- west; and 4) dramatic drying in southwestern United States. In addition to classic hydrometrics, trend analysis was performed on Latent Features (LFs), which were extracted by Variation AutoEncoder (VAE) from raw streamflow data and are considered “machine-learned hydrometrics”. Some LFs with direct hydrological implications were closely associated with the classical hydrometric indicators such as flow quantity, seasonal distribution, timing and magnitude of freshet, and snow- to-rain transition. The changing patterns of streamflows revealed by LFs show direct agreement with the hydrometric trends. By reconstructing hydrographs from select LFs, VAE also provides a mechanism to project changes in streamflow patterns in the future. Furthermore, a parametric t-SNE method based on DL technology was developed to visualize similarity among a large number of hydro- graphs on a 2-D map. This novel method allowed fast grouping of hydrologically similar rivers based on their flow regime type and provides new opportunities for streamflow classification and regionalization. Thesis Doctor of Philosophy (PhD)

Objective Functional vein end to arterial side (ETS) anastomosis uses vein side to arterial side (STS) anastomosis with distal vein ligation, which can achieve similar effects as those of ETS after STS anastomosis. The purpose of the study was to provide a meta-analysis to compare the clinical outcomes between traditional and functional ETS anastomosis in radiocephalic fistula for dialysis access. Methods Databases including PubMed, EMbase, the Cochrane Library, CNKI, Wanfang database were searched from the inception to February 6, 2020. Eligible studies comparing traditional and functional ETS anastomosis in radiocephalic fistula were included. Data were analyzed using Review Manager Version 5.3. Results Seven studies were included in the meta-analysis. Five randomized controlled trials and two cohort studies involving 841 patients were identified. Compared with traditional ETS anastomosis, functional ETS anastomosis had shorter anastomosis time (MD − 9.54, 95% CI − 17.96 to − 1.12, P = 0.03), higher surgical success rate (OR 3.80, 95% CI 1.76–8.22, P P P = 0.03), higher patency rate after 6 months (OR 1.90, 95%CI 1.09–3.31, P = 0.02), higher patency rate after 12 months (OR 1.70, 95% CI 1.09–2.66, P = 0.02). There was no difference after the two arteriovenous (AVF) anastomosisl methods concerning AVF maturation time (SMD − 0.48, 95% CI − 1.30–0.34, P = 0.25) and patency rate after 1 month (OR 1.77, 95% CI 0.65–4.80, P = 0.26). Conclusion Functional ETS anastomosis had advantages of easy operation, high surgical success rate, few complications, high patency rate of 3 months and long-term, but did not have obvious advantage in the early stages concerning AVF maturation time and 1-month patency rate.

Background: The objective of this study was to compare the complications of low-site peritoneal dialysis (PD) catheter placement and traditional open surgery in peritoneal dialysis catheter insertion. Methods: The following databases were searched from inception to September 6, 2019: PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure, and Wanfang. Eligible studies comparing low-site PD catheter placement and traditional open surgery in peritoneal dialysis catheter insertion were included. The data were analyzed using Review Manager Version 5.3. Results: Seven studies were included in the meta-analysis. A total of 504 patients were included in the low-site PD catheter placement group, and 325 patients were included in the traditional open surgery group. Compared with traditional open surgery, low-site PD catheter placement had a lower incidence rate of catheter displacement (odds ratios [OR] 0.11, 95% CI 0.05–0.22, P

Understanding the nature of streamflow response to precipitation inputs is at the core of applied hydrological applications such as flood forecasting and water resource management. Indices such as the runoff ratio, recession constant and response time of a watershed retain an important place in hydrology decades after their establishment as metrics to compare watersheds and understand the impact of human activity, geology, geomorphology, soils and climate on precipitation-runoff relations. Extracting characteristics of the hyetograph-hydrograph relationship is often done manually, resulting in subjective and inconsistent results that require considerable time. In addition, there are a large number of metrics proposed to analyze the hyetograph-hydrograph relationship and hydrograph shape that are typically subjective in application. The objective of this research is to develop an automated and flexible toolkit for rainfall-runoff analysis. Using the MATLAB language, a series of inter-related functions are created to extract rainfall-runoff events from time-series of rainfall and streamflow data and compute commonly used characteristics of the hyetograph-hydrograph relationship. Furthermore, a number of input parameters are introduced to add flexibility to the toolkit. This toolkit has been applied successfully to four watersheds in Canada and Scotland. A subsequent analysis was performed assessing the sensitivity of parameter selection on the toolkit performance, and a number of suggestions for users provided. It is anticipated that this toolkit will provide hydrologists with a rapid objective method of analyzing rainfall and runoff data where in the past manual procedures resulted in considerable subjectivity in results. Thesis Master of Science (MSc)