scholarly journals Paleo-hydrologic reconstruction of 400 years of past flows at a weekly time step for major rivers of Western Canada

2019 ◽  
Author(s):  
Andrew R. Slaughter ◽  
Saman Razavi
Keyword(s):  
Time Series ◽  
Water Resources ◽  
Tree Ring ◽  
Flow Distribution ◽  
Future Climate Change ◽  
Western Canada ◽  
Tree Ring Chronology ◽  
Time Step ◽  
Water Resources Systems ◽  
Tree Ring Data

Abstract. The assumption of stationarity in water resources no longer holds, particularly within the context of future climate change. Plausible scenarios of flows that fluctuate outside the envelope of variability of the gauging data are required to assess the robustness of water resources systems to future conditions. This study presents a novel method of generating weekly-time-step flows based on tree-ring chronology data. Specifically, this method addresses two long-standing challenges with paleo-reconstruction: (1) the typically limited predictive power of tree-ring data at the annual and sub-annual scale, and (2) the inflated short-term persistence in tree-ring time series and improper use of prewhitening. Unlike the conventional approach, this method establishes relationships between tree-ring chronologies and naturalised flow at a biennial scale to preserve persistence properties and variability of hydrological time series. Biennial flow reconstructions are further disaggregated to weekly, according to the weekly flow distribution of reference two-year instrumental periods, identified as periods with broadly similar tree-ring properties to that of every two-year paleo-period. The Saskatchewan River Basin (SaskRB), a major river in Western Canada, is selected as a study area, and weekly flows in its four major tributaries are extended back to the year 1600. The study shows that the reconstructed flows properly preserve the statistical properties of the reference flows, particularly, short- to long-term persistence and the structure of variability across time scales. An ensemble approach is presented to represent the uncertainty inherent in the statistical relationships and disaggregation method. The ensemble of reconstructed weekly flows are publically available for download from https://doi.org/10.20383/101.0139 (Slaughter and Razavi, 2019).

scholarly journals Paleo-hydrologic reconstruction of 400 years of past flows at a weekly time step for major rivers of Western Canada

2020 ◽  
Vol 12 (1) ◽  
pp. 231-243
Author(s):  
Andrew R. Slaughter ◽  
Saman Razavi
Keyword(s):  
Time Series ◽  
Tree Ring ◽  
Flow Distribution ◽  
Future Climate Change ◽  
Western Canada ◽  
Tree Ring Chronology ◽  
Time Step ◽  
Persistence Properties ◽  
Tree Ring Data ◽  
Improper Use

Abstract. The assumption of stationarity in water resources no longer holds, particularly within the context of future climate change. Plausible scenarios of flows that fluctuate outside the envelope of variability of the gauging data are required to assess the robustness of water resource systems to future conditions. This study presents a novel method of generating weekly time step flows based on tree-ring chronology data. Specifically, this method addresses two long-standing challenges with paleo-reconstruction: (i) the typically limited predictive power of tree-ring data at the annual and sub-annual scale and (ii) the inflated short-term persistence in tree-ring time series and improper use of pre-whitening. Unlike the conventional approach, this method establishes relationships between tree-ring chronologies and naturalized flow at a biennial scale to preserve persistence properties and variability of hydrological time series. Biennial flow reconstructions are further disaggregated to weekly flow reconstructions, according to the weekly flow distribution of reference 2-year instrumental periods, identified as periods with broadly similar tree-ring properties to those of every 2-year paleo-period. The Saskatchewan River basin (SaskRB) in Western Canada is selected as a study area, and weekly flows in its four major tributaries are extended back to the year 1600. The study shows that the reconstructed flows properly preserve the statistical properties of the reference flows, particularly in terms of short- to long-term persistence and the structure of variability across timescales. An ensemble approach is presented to represent the uncertainty inherent in the statistical relationships and disaggregation method. The ensemble of reconstructed weekly flows are publicly available for download from https://doi.org/10.20383/101.0139 (Slaughter and Razavi, 2019).

Recent growth increases in old-growth longleaf pine

1993 ◽  
Vol 23 (5) ◽  
pp. 846-853 ◽  
Author(s):  
D.C. West ◽  
T.W. Doyle ◽  
M.L. Tharp ◽  
J.J. Beauchamp ◽  
W.J. Platt ◽  
...  
Keyword(s):  
Tree Ring ◽  
Longleaf Pine ◽  
Biomass Accumulation ◽  
Severity Index ◽  
Drought Severity ◽  
Tree Ring Chronology ◽  
Annual Increment ◽  
Old Growth ◽  
Tree Ring Data ◽  
Old Trees

Longleaf pine (Pinuspalustris Mill.) tree-ring data were obtained from an old-growth stand located in Thomas County, Georgia. The tree-ring chronology from the pine stand is composed of a collection of cores extracted from 26 trees ranging in age from approximately 100 to 400 years. These cores were prepared, dated, and measured, and the resulting data were examined with dendrochronological and statistical techniques. Beginning in approximately 1950 and continuing to the present, annual increments of all age classes examined in this study have increased, resulting in an average annual ring increment approximately 40% greater in 1987 than in 1950. When compared with expected annual increment, the increase for 100- to 150-year-old trees is approximately 45%, while the increase for 200- to 400-year-old trees is approximately 35%. In terms of stand-level aboveground biomass accumulation, the increased growth has resulted in approximately 5% more biomass than expected. The increased growth cannot be explained by disturbance; stand history; or trends in precipitation, temperature, or Palmer drought severity index over the last 57 years. Increased atmospheric CO2 is a possible explanation for initiation of the observed trend, while SOx and NOx may be augmenting continuation of this phenomenon.

scholarly journals Juniper Tree-Ring Data from the Kuramin Range (Northern Tajikistan) Reveals Changing Summer Drought Signals in Western Central Asia

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 505 ◽  
Author(s):  
Feng Chen ◽  
Tongwen Zhang ◽  
Andrea Seim ◽  
Shulong Yu ◽  
Ruibo Zhang ◽  
...  
Keyword(s):  
Central Asia ◽  
Tree Ring ◽  
Large Scale ◽  
Southern Oscillation ◽  
Severity Index ◽  
Drought Severity ◽  
Summer Drought ◽  
Tree Ring Chronology ◽  
Tree Ring Data ◽  
June July

Coniferous forests cover the mountains in many parts of Central Asia and provide large potentials for dendroclimatic studies of past climate variability. However, to date, only a few tree-ring based climate reconstructions exist from this region. Here, we present a regional tree-ring chronology from the moisture-sensitive Zeravshan juniper (Juniperus seravschanica Kom.) from the Kuramin Range (Tajikistan) in western Central Asia, which is used to reveal past summer drought variability from 1650 to 2015 Common Era (CE). The chronology accounts for 40.5% of the variance of the June–July self-calibrating Palmer Drought Severity Index (scPDSI) during the instrumental period (1901 to 2012). Seven dry periods, including 1659–1696, 1705–1722, 1731–1741, 1758–1790, 1800–1842, 1860–1875, and 1931–1987, and five wet periods, including 1742–1752, 1843–1859, 1876–1913, 1921–1930, and 1988–2015, were identified. Good agreements between drought records from western and eastern Central Asia suggest that the PDSI records retain common drought signals and capture the regional dry/wet periods of Central Asia. Moreover, the spectral analysis indicates the existence of centennial (128 years), decadal (24.3 and 11.4 years), and interannual (8.0, 3.6, 2.9, and 2.0 years) cycles, which may be linked with climate forces, such as solar activity and El Niño-Southern Oscillation (ENSO). The analysis between the scPDSI reconstruction and large-scale atmospheric circulations during the reconstructed extreme dry and wet years can provide information about the linkages of extremes in our scPDSI record with the large-scale ocean–atmosphere–land circulation systems.

Optimizing the management of complex water resources systems taking into account the long-term persistence in streamflow

2020 ◽  
Author(s):  
Amaury Tilmant ◽  
Vahid Espanmanesh
Keyword(s):  
Time Series ◽  
Water Resources ◽  
Optimization Techniques ◽  
Irrigated Agriculture ◽  
Water Resources Systems ◽  
Trade Offs ◽  
Conflicting Objectives ◽  
Operating Policies ◽  
Dual Dynamic Programming

<p>The operation of multireservoir systems is a challenging decision-making problem due to (i) multiple, often conflicting, objectives (e.g. hydropower generation versus irrigated agriculture), (ii) stochastic variables (e.g. inflows, water demands, commodity prices), (iii) nonlinear relationships, (e.g. hydropower production function) and (iv) trade-offs between immediate and future consequences. Properly capturing the properties of the hydrologic processes responsible for the inflows is of paramount importance to enhance the performance of water resources systems. This becomes all the more relevant since low-frequency climate signals, which affect the hydrology in numerous regions around the globe, has increased in recent years. If traditional time series models generally fail to reproduce this regime-like behavior, so are the optimization models that are used to support multireservoir operation. Hidden Markov Model (HMM) is a class of hydrological models that can accommodate both overdispersion and serial dependence in historical time series, two essential hydrological properties that must be captured when modeling a system where the climate is switching between different states (e.g., dry, normal, wet). In terms of reservoir operation, Stochastic Dual Dynamic Programming (SDDP) is one of the few optimization techniques that can accomodate both system and hydrologic complexity. In SDDP, the hydrologic uncertainty is often captured by a multi-site periodic autoregressive (MPAR) model. However, MPAR models are unable to represent the long-term persistence of the streamflow process found in some regions, which may lead to suboptimal reservoir operating policies. We present an extension of the SDDP algorithm that can handle the long-term persistence and provide reservoir operating policies that explicitly capture regime shifts. To achieve this, the state-space vector now includes a climate variable whose transition is governed by a HMM. The Senegal River Basin (SRB), whose flow regime is characterized by multiyear dry/wet periods, is used as a case study.</p>

scholarly journals REFINEMENT OF CONIFER GROWTH MODELS BASED ON TREE-RING CHRONOLOGIES OF THE NORTH OF WESTERN SIBERIA

2020 ◽  
pp. 41-48
Author(s):  
V. R. Tsibulsky ◽  
I. G. Solovyev ◽  
D. A. Govorkov
Keyword(s):  
Time Series ◽  
Tree Ring ◽  
Growth Model ◽  
Western Siberia ◽  
Growth Function ◽  
Climate Conditions ◽  
The North ◽  
Tree Ring Data ◽  
Model Update ◽  
Pine Trees

The subject of this research is conifer growth model based on time-series of annual rings width. The article addresses processing of data and model update in respect of forest dendrology. The purpose of study is to update the conifer growth model due to expansion of time-series of tree-rings width in regards to conifer forests in Western Siberia. The method represents expansion of time-series due to the fact that some growth phases had not been taken into account. When measurements were taken at the height of 1.3 meters, the following phases were not considered: seedling, juvenile, immature and beginning of virginile phase. The authors carried out examination of a number of scans and core samples, as well as time-series received by other scientists and which are contained in the International Tree-Ring Data Bank. Based on the results of field studies, the authors recommend to add some zeroes to the beginning of time-series within the range of 10-15 years for pine-trees in the south of Western Siberia, depending on growth conditions; the range of 15-30 years in the north for larch-trees and pine-trees depending on soil and climate conditions and latitude. The sequence of data pre-processing operations for time-series, received by means of core sampling, is as follows: averaging out of radius gain in 2 (3) mutually perpendicular directions for one specimen, graphing of radius gain curve, adding to the beginning of time-series, its normalization, approximation by specified growth function. It is possible to build area growth function for the scans. For averaging out a group of model trees, the sequence of operations is as follows: synchronization of time-series by cross-correlation method, approximation by specified growth function. Methods and results of studies can be applied in forest sectors and oil and gas industries for monitoring of forest health conditions. The proposed method of curve growth model update will allow to define more precisely time intervals for efficient forest exploitation as well as to reconstruct digital models of conifer populations in the north of Western Siberia.

scholarly journals Multi-century lake area changes in the Andean high-elevation ecosystems of the Southern Altiplano

2015 ◽  
Vol 11 (3) ◽  
pp. 1821-1855 ◽  
Author(s):  
M. S. Morales ◽  
J. Carilla ◽  
H. R. Grau ◽  
R. Villalba
Keyword(s):  
Water Resources ◽  
Tree Ring ◽  
High Elevation ◽  
Multiple Time Scales ◽  
Past Century ◽  
Multiple Time ◽  
Lake Area ◽  
Tropical Andes ◽  
Tree Ring Chronology ◽  
Annual Variations

Abstract. High-elevation endorreic lakes in the Southern Altiplano of South America represent a major source of local biodiversity. Size and depth of wetlands in Northwest Argentine (NWA) and Southwest Bolivia (SWB) have shown to be very sensitive to basin hidrological balances, and consequently, very vulnerable to deleterious effects from climate changes. The management of these water resources requires a comprehensive knowledge of their natural variability over multiple time scales. In this study we present a multi-century reconstruction of past lake-area fluctuations in the NWA and SWB, inferred from Polylepis tarapacana tree-ring records. Between 1975 and 2009 interannual lake area fluctuations from nine lakes were quantified based on Landsat satellite images. A composite P. tarapacana tree-ring chronology was developed. Correlations analyses were performed to screen potential predictor tree-ring chronologies for reconstruction models. Inter-annual lake area fluctuations were positively correlated with inter-annual variations of the radial growth of P. tarapacana. A tree-ring chronology (601 years long) was use as predictor, in a regression model, to reconstruct the annual (January–December) mean lake area from nine endorreic lakes. The chronology captures 60% of the total variance in lake-area fluctuations and shows adequate levels of cross-validation. The twentieth century was unusual in the long-term context provided by the reconstruction; a persistent negative trend in lake area is clear in the reconstruction during the past century and is consistent with glacier retreat and other climate proxies from the Altiplano and tropical Andes. These results provide a baseline for the historical range of variability in lake fluctuations, and thus should be considered for the management of biodiversity and water resources in the region, particularly in relation to future XXI century climate scenarios.

Analysis of Tree Ring Data Using the Kalman Filter Technique

IAWA Journal ◽  
1986 ◽  
Vol 7 (4) ◽  
pp. 289-297 ◽  
Author(s):  
Hans Visser
Keyword(s):  
Tree Ring ◽  
Multiple Regression Model ◽  
Model Parameters ◽  
Tree Ring Chronology ◽  
Forecast Performance ◽  
Filter Technique ◽  
Tree Ring Data ◽  
Kaiman Filter ◽  
Weather Parameters ◽  
Weather Variations

A statistical mcthod is presented to filter the influence of weather variations out of a tree ring chronology. The Kaiman filter technique is introduced to estimate a multiple regression model with stochastically fluctuating weather parameters. It cnables the detection of any change in response of trees to weather. The method is in two ways an improvement upon the frequentIy used method of response functions: I) it is not necessary to assume constant model parameters, and 2) the estimation process is not based on the fitting but on the forecast performance of the model.

scholarly journals Qualitative Approach for Assessing Runoff Temporal Dependence Through Geometrical Symmetry

2020 ◽  
Author(s):  
Santiago Zazo Del dedo ◽  
Hector Macian-Sorribes ◽  
Cristina Maria Sena Fael ◽  
Ana-María Garía-Martín ◽  
Jose-Luis Molina ◽  
...  
Keyword(s):  
Time Series ◽  
Water Resources ◽  
Iberian Peninsula ◽  
River Basin ◽  
Causal Reasoning ◽  
Qualitative Approach ◽  
Time Step ◽  
Temporal Dependence ◽  
Temporal Behaviour ◽  
Runoff Change

Currently, noticeable changes in traditional hydrological patterns are being observed on the short and medium-term. These modifications are adding a growing variability on water resources behaviour, especially evident in its availability. Consequently, for a better understanding/knowledge of temporal alterations, it is crucial to develop  new analytical strategies which are capable of capturing these modifications on its temporal behaviour. This challenge is here addressed via a purely stochastic methodology on annual runoff time series. This is performed through the propagation of temporal dependence strength over the time, by means of Causality, supported by Causal Reasoning (Bayes’ theorem), via the relative percentage of runoff change that a time-step produces on the following ones. The result is a dependence mitigation graph, whose analysis of its symmetry provides an innovative qualitative approach to assess time-dependency from a dynamic and continuous perspective against the classical, static and punctual result that a correlogram offers. This was evaluated/applied to four Spanish unregulated river sub-basins; firstly on two Douro/Duero River Basin exemplary case studies (the largest river basin at Iberian Peninsula) with a clearly opposite temporal behaviour, and subsequently applied to two watersheds belonging to Jucar River Basin (Iberian Peninsula Mediterranean side), characterised by suffering regular drought conditions. Keywords: Causal reasoning, Theorem of Bayes, Temporal dependence propagation, Runoff time series, Water resources management

The Potential of Deriving Tree-Ring-Based Field Reconstructions of Droughts and Pluvials over Fennoscandia*,+

2015 ◽  
Vol 28 (9) ◽  
pp. 3453-3471 ◽  
Author(s):  
Kristina Seftigen ◽  
Edward R. Cook ◽  
Hans W. Linderholm ◽  
Mauricio Fuentes ◽  
Jesper Björklund
Keyword(s):  
Tree Ring ◽  
Regional Scale ◽  
Ring Width ◽  
Warm Season ◽  
Contour Method ◽  
Future Climate Change ◽  
Local Regression ◽  
Temperature And Precipitation ◽  
Tree Ring Data ◽  
Moisture Variability

Abstract Moisture availability has been identified as one of the most important factors in the context of future climate change. This paper explores the potential of applying a multiproxy approach to dendroclimatology to infer the twentieth-century moisture variability over Fennoscandia. Fields of the warm-season (June–August) standardized precipitation evapotranspiration index (SPEI) were developed from a dense network of precipitation-sensitive annually resolved tree-ring width (TRW), maximum density (MXD), and stable carbon (δ13C) and oxygen (δ18O) isotope chronologies using a point-by-point local regression technique (PPR). Two different approaches were tested for selecting candidate tree-ring predictors of SPEI for each gridpoint reconstruction: a search radius method and a search spatial correlation contour method. As confirmed by a range of metrics of reconstruction fidelity, both methods produced reconstructions showing a remarkably high accuracy in a temporal sense, but with some minor regional differences. As a whole, the spatial skill of the reconstructed fields was generally quite good, showing the greatest performance in the central and southern parts of the target region. Lower reconstruction skills were observed in northern part of the study domain. Regional-scale moisture anomalies were best captured by the reconstructions, while local-scale features were not as well represented. The authors speculate that a spatially and temporally varying tree-ring proxy response to temperature and precipitation in the region may cause some uncertainties in a Fennoscandian hydroclimatic reconstruction; this needs further investigation. Overall, this study shows a great potential for making long-term spatiotemporal reconstructions of moisture variability for the Fennoscandian region using tree-ring data.

scholarly journals Streamflow variability over 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and on geopotential height field reanalysis

2016 ◽  
Author(s):  
P. Brigode ◽  
F. Brissette ◽  
A. Nicault ◽  
L. Perreault ◽  
A. Kuentz ◽  
...  
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Tree Ring ◽  
Tree Rings ◽  
Geopotential Height ◽  
Climatic Reconstruction ◽  
Daily Streamflow ◽  
Tree Ring Data ◽  
Streamflow Variability ◽  
Climatic Time Series

Abstract. Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir to compare the obtained streamflow series and study the natural streamflow variability over the 1881–2011 period. This new reconstruction is based, not on natural proxies, but on a historical reanalysis of global geopotential height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall-runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, both in terms of monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows, and the other one on spring floods. In terms of mean annual flows, the interannual variability of the reconstructed flows were similar (except for the 1930–1940 decade), with significant changes seen in wetter and drier years. For spring floods, the interannual variabilities reconstructed were quite similar for the 1955–2011 period, but significantly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions, and finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

Sign in / Sign up

Export Citation Format

Share Document