Annual, seasonal and monthly rainfall trend analysis in the Tafna watershed, Algeria

AbstractScientists, since a long time, have paid attention on climate change and, in particular, rainfall decrease. These changes have resulted in modifications of the rainfall regime in many Mediterranean regions. This work is based on monthly rainfall data from 17 stations located in the Tafna catchment (North West of Algeria). The study aim is to identify long-term (1970–2016) spatial and temporal trends in annual, seasonal and monthly precipitation, using the innovative trend analysis (ITA) method. The approach is used to classify trends into “low”, “medium”, “high”, which should be taken in consideration in future studies on floods (“high”) and drought (“low”). The monthly rainfall shows a decreasing trend in all studied stations (100% of stations) during February, March, April, and May, the same phenomenon observed in the majority of stations for June, July (82% of stations), and December (58% of stations). Seasonal analysis indicates a downward trend in winter and spring. Using annual rainfall, the stations located in the north, west and central part of the Tafna show a decrease in rainfall (59% of stations).

Download Full-text

Regionalization of monthly rainfall erosivity patterns in Switzerland

Hydrology and Earth System Sciences ◽

10.5194/hess-20-4359-2016 ◽

2016 ◽

Vol 20 (10) ◽

pp. 4359-4373 ◽

Cited By ~ 17

Author(s):

Simon Schmidt ◽

Christine Alewell ◽

Panos Panagos ◽

Katrin Meusburger

Keyword(s):

Monthly Rainfall ◽

Annual Rainfall ◽

Rainfall Erosivity ◽

Monthly Precipitation ◽

Spatial And Temporal Patterns ◽

Erosion Risk ◽

Explanatory Variables ◽

R Factor ◽

June July ◽

Leave One Out

Abstract. One major controlling factor of water erosion is rainfall erosivity, which is quantified as the product of total storm energy and a maximum 30 min intensity (I30). Rainfall erosivity is often expressed as R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). As rainfall erosivity is closely correlated with rainfall amount and intensity, the rainfall erosivity of Switzerland can be expected to have a regional characteristic and seasonal dynamic throughout the year. This intra-annual variability was mapped by a monthly modeling approach to assess simultaneously spatial and monthly patterns of rainfall erosivity. So far only national seasonal means and regional annual means exist for Switzerland. We used a network of 87 precipitation gauging stations with a 10 min temporal resolution to calculate long-term monthly mean R-factors. Stepwise generalized linear regression (GLM) and leave-one-out cross-validation (LOOCV) were used to select spatial covariates which explain the spatial and temporal patterns of the R-factor for each month across Switzerland. The monthly R-factor is mapped by summarizing the predicted R-factor of the regression equation and the corresponding residues of the regression, which are interpolated by ordinary kriging (regression–kriging). As spatial covariates, a variety of precipitation indicator data has been included such as snow depths, a combination product of hourly precipitation measurements and radar observations (CombiPrecip), daily Alpine precipitation (EURO4M-APGD), and monthly precipitation sums (RhiresM). Topographic parameters (elevation, slope) were also significant explanatory variables for single months. The comparison of the 12 monthly rainfall erosivity maps showed a distinct seasonality with the highest rainfall erosivity in summer (June, July, and August) influenced by intense rainfall events. Winter months have the lowest rainfall erosivity. A proportion of 62 % of the total annual rainfall erosivity is identified within four months only (June–September). The highest erosion risk can be expected in July, where not only rainfall erosivity but also erosivity density is high. In addition to the intra-annual temporal regime, a spatial variability of this seasonality was detectable between different regions of Switzerland. The assessment of the dynamic behavior of the R-factor is valuable for the identification of susceptible seasons and regions.

Download Full-text

Geochemical and isotopic evidence of groundwater salinization processes in the Essaouira region, north-west coast, Morocco

SN Applied Sciences ◽

10.1007/s42452-021-04623-3 ◽

2021 ◽

Vol 3 (7) ◽

Author(s):

Otman EL Mountassir ◽

Mohammed Bahir ◽

Driss Ouazar ◽

Abdelghani Chehbouni ◽

Paula M. Carreira

Keyword(s):

Groundwater Recharge ◽

West Coast ◽

Exchange Process ◽

Environmental Isotopes ◽

Annual Rainfall ◽

Groundwater Salinization ◽

Rock Interaction ◽

North West ◽

The North ◽

Water Rock Interaction

AbstractThe city of Essaouira is located along the north-west coast of Morocco, where groundwater is the main source of drinking, domestic and agricultural water. In recent decades, the salinity of groundwater has increased, which is why geochemical techniques and environmental isotopes have been used to determine the main sources of groundwater recharge and salinization. The hydrochemical study shows that for the years 1995, 2007, 2016 and 2019, the chemical composition of groundwater in the study area consists of HCO3–Ca–Mg, Cl–Ca–Mg, SO4–Ca and Cl–Na chemical facies. The results show that from 1995 to 2019, electrical conductivity increased and that could be explained by a decrease in annual rainfall in relation to climate change and water–rock interaction processes. Geochemical and environmental isotope data show that the main geochemical mechanisms controlling the hydrochemical evolution of groundwater in the Cenomanian–Turonian aquifer are the water–rock interaction and the cation exchange process. The diagram of δ2H = 8 * δ18O + 10 shows that the isotopic contents are close or above to the Global Meteoric Water Line, which suggests that the aquifer is recharged by precipitation of Atlantic origin. In conclusion, groundwater withdrawal should be well controlled to prevent groundwater salinization and further intrusion of seawater due to the lack of annual groundwater recharge in the Essaouira region.

Download Full-text

An Analysis of Long-Term Rainfall Trends and Variability in the Uttarakhand Himalaya Using Google Earth Engine

Remote Sensing ◽

10.3390/rs12040709 ◽

2020 ◽

Vol 12 (4) ◽

pp. 709 ◽

Cited By ~ 3

Author(s):

Abhishek Banerjee ◽

Ruishan Chen ◽

Michael E. Meadows ◽

R.B. Singh ◽

Suraj Mal ◽

...

Keyword(s):

River Basin ◽

Temporal Trends ◽

Google Earth ◽

Monthly Rainfall ◽

Annual Rainfall ◽

Google Earth Engine ◽

Spatio Temporal ◽

Uttarakhand Himalaya ◽

Rainy Days

This paper analyses the spatio-temporal trends and variability in annual, seasonal, and monthly rainfall with corresponding rainy days in Bhilangana river basin, Uttarakhand Himalaya, based on stations and two gridded products. Station-based monthly rainfall and rainy days data were obtained from the India Meteorological Department (IMD) for the period from 1983 to 2008 and applied, along with two daily rainfall gridded products to establish temporal changes and spatial associations in the study area. Due to the lack of more recent ground station rainfall measurements for the basin, gridded data were then used to establish monthly rainfall spatio-temporal trends for the period 2009 to 2018. The study shows all surface observatories in the catchment experienced an annual decreasing trend in rainfall over the 1983 to 2008 period, averaging 15.75 mm per decade. Analysis of at the monthly and seasonal trend showed reduced rainfall for August and during monsoon season as a whole (10.13 and 11.38 mm per decade, respectively); maximum changes were observed in both monsoon and winter months. Gridded rainfall data were obtained from the Climate Hazard Infrared Group Precipitation Station (CHIRPS) and Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR). By combining the big data analytical potential of Google Earth Engine (GEE), we compare spatial patterns and temporal trends in observational and modelled precipitation and demonstrate that remote sensing products can reliably be used in inaccessible areas where observational data are scarce and/or temporally incomplete. CHIRPS reanalysis data indicate that there are in fact three significantly distinct annual rainfall periods in the basin, viz. phase 1: 1983 to 1997 (relatively high annual rainfall); phase 2: 1998 to 2008 (drought); phase 3: 2009 to 2018 (return to relatively high annual rainfall again). By comparison, PERSIANN-CDR data show reduced annual and winter precipitation, but no significant changes during the monsoon and pre-monsoon seasons from 1983 to 2008. The major conclusions of this study are that rainfall modelled using CHIRPS corresponds well with the observational record in confirming the decreased annual and seasonal rainfall, averaging 10.9 and 7.9 mm per decade respectively between 1983 and 2008, although there is a trend (albeit not statistically significant) to higher rainfall after the marked dry period between 1998 and 2008. Long-term variability in rainfall in the Bhilangana river basin has had critical impacts on the environment arising from water scarcity in this mountainous region.

Download Full-text

Spatial and temporal variation in precipitation at the start of the rainy season in tropical Australia

The Rangeland Journal ◽

10.1071/rj09083 ◽

2010 ◽

Vol 32 (2) ◽

pp. 215 ◽

Cited By ~ 13

Author(s):

S. T. Garnett ◽

G. Williamson

Keyword(s):

Seed Germination ◽

El Niño ◽

Rainy Season ◽

El Nino ◽

Southern Oscillation ◽

Temporal Trends ◽

Spatial And Temporal Variation ◽

Economic Implications ◽

North West ◽

The North

The patterns of rainfall early in the rainy season vary substantially across northern Australia, even in sites with the same annual average. This has biophysical and economic implications in terms of land and infrastructure management, resource availability and capacity, and access. Daily patterns in long-term rainfall records in Australia north of 23°S subject to regular monsoonal rainfall were compared with threshold levels for dryland and wetland seed germination, initiation of the growing season, patterns of gaps between early storms and the heaviness of the first falls, correlations between thresholds, spatial variation in correlation with the Southern Oscillation Index (SOI) and temporal trends in mean threshold dates. The earliest rains sufficient to cause seed germination or generate fresh fodder occur in the north-west of the Northern Territory with the average date being later to the south, east and west. Initial falls of the rainy season are heaviest, however, on Cape York Peninsula so that the time between first falls and saturation is shortest in the east. The probability of extended gaps between rainfall events increased from north to south. When the SOI is taken into account, no change in timing could be detected at the few sites with records of sufficient duration. However, because of changes in SOI frequency, rains are tending to start earlier in the drier parts of the north and north-west and later in the east. This may be because anthropogenic climate change is resulting in fewer classical El Niño Southern Oscillation events and more frequent El Niño Modoki climate anomalies.

Download Full-text

The Sustainable Grazing Systems National Experiment. 1. Introduction and methods

Australian Journal of Experimental Agriculture ◽

10.1071/ea02183 ◽

2003 ◽

Vol 43 (8) ◽

pp. 695 ◽

Cited By ~ 17

Author(s):

M. H. Andrew ◽

G. M. Lodge

Keyword(s):

Data Collection ◽

Western Australia ◽

Annual Rainfall ◽

Single Experiment ◽

Data Set ◽

North West ◽

North East ◽

The North ◽

Grazing Systems ◽

Sustainable Grazing

This paper outlines the development and design of the Sustainable Grazing Systems (SGS) National Experiment from the initial call for expressions of interest, through several workshop processes to the final selection and implementation of its 6 component sites, and the general methodology used at each. Sites were located in Western Australia, western Victoria, north-east Victoria, and on the Central Tablelands, North West Slopes, and the eastern Riverina of New South Wales. Sites in Western Australia, north-east Victoria, the North West Slopes, and the eastern Riverina also had subsites. Methods for the sites and subsites (data collection for pastures, livestock, weather, soils and site characterisation) are presented to provide a central reference, and to save duplication in subsequent papers. Descriptions are provided of the location, average annual rainfall, major pasture, soil and stock types, design and number of treatments, and initial soil levels (0–10 cm) of phosphorus, electrical conductivity, and pH for sites and subsites. Also outlined is the major focus of the research undertaken at each site. While sites studied regionally relevant issues, they operated under a common protocol for data collection with a minimum data set being specified for each of 5 unifying themes: pastures, animal production, water, nutrients, and biodiversity. Economic analyses were also undertaken at the macro- and micro-level, and a procedural tool developed for appraising the on- and off-farm impacts of different systems. To give effect to the themes, common database and modelling tools were developed specifically for the national experiment, so that collectively sites comprised a single experiment.

Download Full-text

The distribution, habitat requirements and conservation status of the plains rat, Pseudomys australis (Rodentia : Muridae)

Wildlife Research ◽

10.1071/wr97060 ◽

1999 ◽

Vol 26 (4) ◽

pp. 463 ◽

Cited By ~ 19

Author(s):

R. Brandle ◽

K. E. Moseby ◽

M. Adams

Keyword(s):

Conservation Status ◽

Single Species ◽

Annual Rainfall ◽

Tissue Samples ◽

North West ◽

The North ◽

Western Lake ◽

Discrete Population ◽

Territory Border ◽

North Western

Species in the Pseudomys australis complex were historically widely distributed in a variety of habitats over southern Australia. By 1990 the group had apparently declined to a single species in the centre of its former range in the north-western Lake Eyre Basin, in gibber plain areas. In the past, the species has been collected only after exceptional annual rainfall. This study sought to define the current distribution of P. australis and to determine its preferred habitats during the usual prolonged dry periods. Allozyme electrophoresis on blood and tissue samples were used to investigate the genetic distinctiveness of geographically separated populations. The known distribution has been extended along a belt of gibber habitats running from north-west of Lake Eyre on the Northern Territory border to south of Lake Eyre South, and a discrete population inhabiting gibber tableland west of Lake Torrens. Pseudomys australis was extant in low-lying patches of deep cracking clay associated with minor drainage features and small depressions of cracking clay ‘gilgai’ common on some gibber plains. The former type sustained significantly denser populations, which we suggest represent ‘source’ habitats or ‘refugia’ during droughts. Many of the 16 localities at which the species was recorded are geographically separated; however, electrophoretic analyses showed high levels of allozyme heterozygosity and no evidence of speciation.

Download Full-text

Annual Rainfall in Pernambuco, Brazil: Regionalities, Regimes, and Time Trends

Revista Brasileira de Meteorologia ◽

10.1590/0102-77863630129 ◽

2021 ◽

Author(s):

Alan Cezar Bezerra ◽

Sidney Anderson Teixeira da Costa ◽

Jhon Lennon Bezerra da Silva ◽

Athos Murilo Queiroz Araújo ◽

Geber Barbosa de Albuquerque Moura ◽

...

Keyword(s):

Trend Analysis ◽

Time Trend ◽

Statistical Significance ◽

Annual Rainfall ◽

Rainfall Regime ◽

Annual Data ◽

Positive Trend ◽

Precipitation Regime ◽

Mean Values ◽

Seasonal Analysis

Abstract This study aimed to identify the homogeneous zones, the regimes, and the local trends for annual and seasonal rainfall in the state of Pernambuco, Brazil. We collected seasonal and annual data on monthly rainfall from 45 weather stations in Pernambuco from 1987 to 2019. The data were organized yearly to identify the homogeneous rainfall zones based on Euclidean distance and Ward's coefficient. The mean annual value of each zone was calculated and the data were subjected to descriptive statistics analysis, analysis of rainfall regime with the Rain Anomaly Index, and time trend analysis using the Mann-Kendall method. The results show three homogeneous rainfall zones: 1 (semiarid), 2 (transition), and 3 (coastal), with mean values for annual rainfall of 562, 1032, and 1812 mm year-1, respectively. The precipitation regime showed the predominance of dry years as zones 1, 2, and 3 exhibited dry periods of 18, 17, and 15 years, respectively. Time trend analysis revealed a decrease in annual rainfall of 48.7 mm for Zone 1, 13.2 mm for Zone 2, and 204.4 mm for Zone 3, without statistical significance. Seasonal analysis demonstrated that Zone 1 presented a negative trend in the spring and a positive trend in Zone 2 in the summer, indicating changes in the rain seasonality.

Download Full-text

Trend Analysis and Variability of Air Temperature and Rainfall in Regional River Basins

Civil Engineering Journal ◽

10.28991/cej-2021-03091692 ◽

2021 ◽

Vol 7 (5) ◽

pp. 816-826

Author(s):

Benjamin Nnamdi Ekwueme ◽

Jonah Chukwuemeka Agunwamba

Keyword(s):

Water Resources ◽

Trend Analysis ◽

Air Temperature ◽

Temporal Trends ◽

Kendall Test ◽

River Basins ◽

Annual Rainfall ◽

Eastern Region ◽

South Eastern ◽

Mann Kendall Test

Global warming and climate variability are emerging as the foremost environmental problems in the 21st century, especially in developing countries. Full knowledge of key climate change variables is crucial in managing water resources in river basins. This study examines the variability of air temperature and rainfall in the five states of South-Eastern region of Nigeria, using the trend analysis approach. For this purpose, temporal trends in annual rainfall and temperature were detected using non-parametric Mann-Kendall test at 5% significance level. The time series rainfall and temperature data for the period 1922-2008 were analyzed statistically for each state separately. The results of Mann Kendall test showed that there is trend in rainfall in all the capital cities in South-East except Owerri and Awka. It is also observed that the trend of rainfall is decreasing for all the study areas in South-East with the lowest trend rate of -0.1153 mm rainfall occurring in Umuahia. In the case of air temperature, it is observed that the trend is increasing for all the study areas in South-East with the highest trend rate of 0.04698 oC/year occurring in Enugu. These findings provide valuable information for assessing the influence of changes on air temperature and rainfall on water resources and references for water management in the South-Eastern river basin of Nigeria. It also proved that Mann-Kendall technique is an effective tool in analyzing temperature and rainfall trends in a regional watershed. Doi: 10.28991/cej-2021-03091692 Full Text: PDF

Download Full-text

Trend Analysis of Annual and Monthly Rainfall in Erbil City, Kurdistan Region, Iraq

Polytechnic Journal ◽

10.25156/ptj.v9n2y2019.pp30-36 ◽

2019 ◽

Vol 9 (2) ◽

pp. 30-36 ◽

Cited By ~ 1

Author(s):

Saud A. Hussien ◽

Basil Y. Mustafa ◽

Farzand K. Medhat

Keyword(s):

Regression Analysis ◽

Linear Regression ◽

Trend Analysis ◽

Linear Regression Analysis ◽

Monthly Rainfall ◽

Annual Rainfall ◽

Sen’S Slope Estimator ◽

Sen’S Slope ◽

Slope Estimator ◽

Non Parametric

The objective of this study is to identify the trend for the annual and monthly rainfall time series data from 1963–1964 to 2018–2019 for Erbil city rainfall gauging station. The trend analysis was conducted for only rainy months (from October to May) using the non-parametric Mann-Kendall test, whereas a non-parametric Sen’s slope estimator was used to determine the magnitude of the trend. A functional relationship has been developed between variables using linear regression analysis to determine a linear trend of rainfall for the study area. The annual trend analysis revealed negative (decreasing) trend because the Kendall’s tau (Z) value and the Sen’s slope estimator magnitude were both negative and found to be −0.093 and −1.37, respectively, and the slope of the linear regression analysis was also negative and equal to −0.9148 mm/year, which represents the rate of yearly annual rainfall decreasing trend. Considering the result of monthly rainfall, the trend analysis of rainfall has suggested that there is a trend variation of rainfall in the rainy months. Further, the analysis revealed a negative (decreasing) trend for months November, January, February, March, April, and May and positive (increasing) trend for months October and December. This study is important as it greatly contributes in water resources system planning and management in this region. Furthermore, the results obtained in this work are promising and might help hydraulic civil and water resource engineers in the design of hydraulic structures.

Download Full-text

Precipitation concentration index (PCI) a tool to evaluate the distribution of Rainfall, Barishal, Bangladesh

International Journal of Advanced Geosciences ◽

10.14419/ijag.v8i2.31074 ◽

2020 ◽

Vol 8 (2) ◽

pp. 193

Author(s):

Sudip Saha

Keyword(s):

Concentration Index ◽

Research Work ◽

Monthly Rainfall ◽

Annual Rainfall ◽

Winter Rainfall ◽

Precipitation Concentration Index ◽

Precipitation Concentration ◽

The Mean ◽

June July ◽

The Right

The present research work reveals the mean annual rainfall of Barishal is 2087.34 mm for the investigated period. The maximum annual rainfall was 3390 mm in the year of 1960 and minimum annual rainfall was recorded as 1277 mm in the year of 1964. The annual rainfall is inversely correlated with time. The maximum monthly rainfall is recorded in the month of July. The amount of annual rainfall is strongly significantly positively correlated with the monthly rainfall of May, June, July, August and September. In Barishal, the value of skewness for all rainfall data are positive that indicate the data are skewed to the right. The positive value of kurtosis of the eleven months of the year (except July) means a peaked distribution and a negative value in the month of July reveals the flat distribution with the same mean and standard deviation. The annual PCI value is inversely proportional to the annual rainfall. The analyses of seasonal precipitation concentration index (SPCI) reveals that the rainfall is uniformly distributed in summer monsoon whereas the winter rainfall shows the dominance of strong irregularity in precipitation distribution.

Download Full-text