Wavelet-based trend analysis of hydrological processes at different timescales

2015 ◽  
Vol 6 (3) ◽  
pp. 414-435 ◽  
Author(s):  
Vahid Nourani ◽  
Nasrin Nezamdoost ◽  
Maryam Samadi ◽  
Farnaz Daneshvar Vousoughi
Keyword(s):  
Time Series ◽  
Trend Analysis ◽  
Stream Flow ◽  
Discrete Wavelet ◽  
Precipitation Data ◽  
Short Term ◽  
Mk Test ◽  
Starting Point ◽  
Annual Time Series ◽  
Annual Time

This study analyzes involved trends in stream flow and precipitation data at monthly, seasonal and annual timescales observed at six precipitation and four stream flow stations of Tampa Bay using non-parametric Mann–Kendall (MK) and discrete wavelet transform (DWT) methods. The MK test and sequential MK analysis were applied to different combinations of DWT after removing the effect of significant lag-1 serial correlation to calculate components responsible for trend of the time series. Also, the sequential MK test was used to find the starting point of changes in annual time series. The results showed that negative trend is prevalent in the case study; generally, short-term periods were important in the involved trend at original time series. Thus, the precipitation data at three scales showed short-term periods of 2 months, 6 months and 2 years in monthly, seasonal and annual scales, respectively. In the greatest stream-flow time series at three timescales, wavelet-based detail at level 2 plus the approximations time series was conceded as the dominant periodic component. Finally, the results of Sen's trend analysis, applied to the original annual time series, also confirmed the results of the proposed wavelet-based MK test in most cases.

scholarly journals Trend Analysis of Annual and Seasonal River Runoff by Using Innovative Trend Analysis with Significant Test

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 95
Author(s):  
Yilinuer Alifujiang ◽  
Jilili Abuduwaili ◽  
Yongxiao Ge
Keyword(s):  
Time Series ◽  
Trend Analysis ◽  
River Runoff ◽  
Temporal Trends ◽  
Temporal Distribution ◽  
Trend Test ◽  
Data Series ◽  
Mk Test ◽  
Comparison Results ◽  
Innovative Trend Analysis

This study investigated the temporal patterns of annual and seasonal river runoff data at 13 hydrological stations in the Lake Issyk-Kul basin, Central Asia. The temporal trends were analyzed using the innovative trend analysis (ITA) method with significance testing. The ITA method results were compared with the Mann-Kendall (MK) trend test at a 95% confidence level. The comparison results revealed that the ITA method could effectively identify the trends detected by the MK trend test. Specifically, the MK test found that the time series percentage decreased from 46.15% in the north to 25.64% in the south, while the ITA method revealed a similar rate of decrease, from 39.2% to 29.4%. According to the temporal distribution of the MK test, significantly increasing (decreasing) trends were observed in 5 (0), 6 (2), 4 (3), 8 (0), and 8 (1) time series in annual, spring, summer, autumn, and winter river runoff data. At the same time, the ITA method detected significant trends in 7 (1), 9 (3), 6(3), 9 (3), and 8 (2) time series in the study area. As for the ITA method, the “peak” values of 24 time series (26.97%) exhibited increasing patterns, 25 time series (28.09%) displayed increasing patterns for “low” values, and 40 time series (44.94%) showed increasing patterns for “medium” values. According to the “low”, “medium”, and “peak” values, five time series (33.33%), seven time series (46.67%), and three time series (20%) manifested decreasing trends, respectively. These results detailed the patterns of annual and seasonal river runoff data series by evaluating “low”, “medium”, and “peak” values.

scholarly journals The impact of forest regeneration on streamflow in 12 mesoscale humid tropical catchments

2013 ◽  
Vol 17 (7) ◽  
pp. 2613-2635 ◽  
Author(s):  
H. E. Beck ◽  
L. A. Bruijnzeel ◽  
A. I. J. M. van Dijk ◽  
T. R. McVicar ◽  
F. N. Scatena ◽  
...  
Keyword(s):  
Time Series ◽  
Land Cover ◽  
Forest Regeneration ◽  
Forest Cover ◽  
Impact Analysis ◽  
Forest Area ◽  
Macro Scale ◽  
Annual Time Series ◽  
The Impact ◽  
Annual Time

Abstract. Although regenerating forests make up an increasingly large portion of humid tropical landscapes, little is known of their water use and effects on streamflow (Q). Since the 1950s the island of Puerto Rico has experienced widespread abandonment of pastures and agricultural lands, followed by forest regeneration. This paper examines the possible impacts of these secondary forests on several Q characteristics for 12 mesoscale catchments (23–346 km2; mean precipitation 1720–3422 mm yr−1) with long (33–51 yr) and simultaneous records for Q, precipitation (P), potential evaporation (PET), and land cover. A simple spatially-lumped, conceptual rainfall–runoff model that uses daily P and PET time series as inputs (HBV-light) was used to simulate Q for each catchment. Annual time series of observed and simulated values of four Q characteristics were calculated. A least-squares trend was fitted through annual time series of the residual difference between observed and simulated time series of each Q characteristic. From this the total cumulative change (Â) was calculated, representing the change in each Q characteristic after controlling for climate variability and water storage carry-over effects between years. Negative values of  were found for most catchments and Q characteristics, suggesting enhanced actual evaporation overall following forest regeneration. However, correlations between changes in urban or forest area and values of  were insignificant (p ≥ 0.389) for all Q characteristics. This suggests there is no convincing evidence that changes in the chosen Q characteristics in these Puerto Rican catchments can be ascribed to changes in urban or forest area. The present results are in line with previous studies of meso- and macro-scale (sub-)tropical catchments, which generally found no significant change in Q that can be attributed to changes in forest cover. Possible explanations for the lack of a clear signal may include errors in the land cover, climate, Q, and/or catchment boundary data; changes in forest area occurring mainly in the less rainy lowlands; and heterogeneity in catchment response. Different results were obtained for different catchments, and using a smaller subset of catchments could have led to very different conclusions. This highlights the importance of including multiple catchments in land-cover impact analysis at the mesoscale.

scholarly journals Trend analysis of water quality parameters for the Nisava river

2013 ◽  
Vol 11 (3) ◽  
pp. 199-210 ◽  
Author(s):  
Milan Gocic ◽  
Slavisa Trajkovic
Keyword(s):  
Water Quality ◽  
Trend Analysis ◽  
Kendall Test ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Total Hardness ◽  
Significance Level ◽  
Annual Series ◽  
Annual Time Series ◽  
Annual Time

The data of 12 water quality parameters have been daily monitored at the Nis station on the Nisava River during 2000-2004. The trend analysis was performed on monthly, seasonal and annual time series using the Mann-Kendall test, the Spearman?s Rho test and the linear regression at the 5% significance level. The monthly results showed that significant trends were found only in pH, total hardness, Ca and SO4 data. The results in seasonal series indicated that the significant trends were detected in pH, total hardness, Cl, Ca and SO4 data. In annual series, the trends were insignificant at the 5% significance level.

scholarly journals Mapping canopy damage from understory fires in Amazon forests using annual time series of Landsat and MODIS data

2011 ◽  
Vol 115 (7) ◽  
pp. 1706-1720 ◽  
Author(s):  
Douglas C. Morton ◽  
Ruth S. DeFries ◽  
Jyoteshwar Nagol ◽  
Carlos M. Souza ◽  
Eric S. Kasischke ◽  
...  
Keyword(s):  
Time Series ◽  
Modis Data ◽  
Annual Time Series ◽  
Annual Time ◽  
Canopy Damage

Using annual time-series of Landsat images to assess the effects of forest restitution in post-socialist Romania

2012 ◽  
Vol 118 ◽  
pp. 199-214 ◽  
Author(s):  
Patrick Griffiths ◽  
Tobias Kuemmerle ◽  
Robert E. Kennedy ◽  
Ioan V. Abrudan ◽  
Jan Knorn ◽  
...  
Keyword(s):  
Time Series ◽  
Landsat Images ◽  
Annual Time Series ◽  
Annual Time

Income and Price Elasticities in India's Trade

1994 ◽  
Vol 19 (2) ◽  
pp. 13-20
Author(s):  
G S Gupta ◽  
H Keshava
Keyword(s):  
Time Series ◽  
Time Series Data ◽  
Series Data ◽  
Individual Country ◽  
Price Elasticities ◽  
The World ◽  
Annual Time Series ◽  
Income And Price Elasticities ◽  
Annual Time

This article by G S Gupta and H Keshava estimates the export and import functions for India both at the aggregate (rest of the world) as well as the important individual country levels using annual time series data for the period 1960-61 through 1990-91.

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