scholarly journals Long Term Trends of Hydrology, Sediment Yield and Crop Productivity in Andit Tid Watershed Central Highlands of Ethiopia

2020 ◽  
Author(s):  
Ayele Desalegn ◽  
Tilahun Getachew ◽  
Temesgen Yilma ◽  
Tilashwork Chanie
Keyword(s):  
Trend Analysis ◽  
Sediment Yield ◽  
Water Conservation ◽  
Crop Production ◽  
Temporal Distribution ◽  
Sediment Concentration ◽  
Spatial And Temporal Distribution ◽  
Sediment Loss ◽  
Long Term Trends

Abstract Background: Previously in Ethiopia reliable climatic and hydro-meteorological data are not available and not maintained properly but the long-term database is needed for the assessment and planning of resource dynamics. To minimize the lack of reliable database, the Soil Conservation Research Program (SCRP) established observatory model watersheds since 1981. Andit tid watershed is one of these watersheds established for monitoring the long term trends of climatic, hydrologic, sediment loss and crop production system as a representative site for central high land parts of Ethiopia at 1982. This research paper compiles the analysis of spatial and temporal distribution of the rain fall; trends of run off and sediment loss and their relation and the influence of position of terraces on crop production. Result: From the rainfall trend analysis result the rainfall of the watershed has insignificant spatial (PCI=1.07) and temporal (CV=16.7%) variation. The precipitation coefficient (%) value of the watershed indicates that July and August have big rain with high concentration; September have big rain with moderate concentration and these three months could contribute more than one twelfth of total rainfall amount. The highest runoff and sediment yield were observed in August and July, while sediment concentration was generally high in June. All crops delivered statistically highest yield (P<0.05) immediately above bunds (zone a). Conclusion: The rainfall spatial and temporal distribution trend analysis results conclude that the watershed is not vulnerable for future drought. The highest sediment concentration occurred in June was because of the reason that the lands are plowed and prepared for crop growth; following this small rainfall can carry much soil and can contribute for high suspended sediment concentration. The highest grain yield obtained from above bunds is because of the trapped and accumulated soil and plant nutrient could contribute for better performance and production of crops. To obtain better crop yield; to minimize sediment loss and improve the stream flow it is better to maintain the existed soil and water conservation structures and apply the new interventions.

scholarly journals Effect of natural rainfall on the migration characteristics of runoff and sediment on purple soil sloping cropland during different planting stages

2021 ◽  
Author(s):  
Yi Wang ◽  
Jiupai Ni ◽  
Chengsheng Ni ◽  
Sheng Wang ◽  
Deti Xie
Keyword(s):  
Sediment Yield ◽  
Soil Loss ◽  
Heavy Rain ◽  
Sediment Concentration ◽  
Purple Soil ◽  
Torrential Rain ◽  
Sediment Yields ◽  
Natural Rainfall ◽  
Sediment Loss ◽  
Rain Events

Abstract Due to the difficulty in monitoring subsurface runoff and sediment migration, their loss loads are still not clear and need further study. This study monitored water and soil loss occurring within experimental field plots for two calendar years under natural rainfall events. The sediment loss load was quantified by considering the corresponding water flow flux and its sediment concentration. The results showed that 60.04% of the runoff and 2.83% of the sediment were lost underground. The annual underground sediment loss reached up to 54.6 kg*ha−1*yr−1. A total of 69.68% of the runoff yield and 67.25% of the sediment yield were produced during the corn planting stage (CPS: March–July). Heavy rain and torrential rain events produced 94.45%, 65.46% of the annual runoff and 94.45%, 76.21% of the sediment yields during the corn-planting stage and summer fallow period (SFP: August–September). The rain frequency, rainfall, and rainfall duration of each planting stage significantly affected the resulting runoff and sediment yield. Measures aimed at the prevention and control of water-soil loss from purple soil sloping land should heavily focus on torrential rain and heavy rain events during the CPS and SFP. This paper aims to provide a practical reference for quantifying the water and soil loss from purple soil sloping cropland.

scholarly journals Impact of earthquake-triggered landslides on catchment sediment yield

2015 ◽  
Vol 367 ◽  
pp. 291-296
Author(s):  
M. Vanmaercke ◽  
F. Obreja ◽  
J. Poesen
Keyword(s):  
Sediment Yield ◽  
Seismic Activity ◽  
Fold Increase ◽  
Sediment Concentration ◽  
Spatial And Temporal Variation ◽  
Strongly Correlated ◽  
Before And After ◽  
Sediment Export

Abstract. This study explores the role of seismic activity in explaining spatial and temporal variation in sediment export from the Siret basin in Romania. Based on long-term (>30 years) sediment export measurements for 38 subcatchments, we found that spatial variation in sediment yield (SY) is strongly correlated to the degree of seismic activity and catchment lithology. Combined, these factors explain 80% of the variation in SY. To investigate the role of earthquake-triggered landslides in explaining these correlations, we studied the temporal variability in sediment concentrations before and after the 7.4 Mw earthquake of 1977 for ten subcatchments. Despite the fact that this earthquake triggered many landslides, only one subcatchment showed a clear (3-fold) increase in sediment concentration per unit discharge after the earthquake. This shows that, although prolonged seismic activity strongly controls average SY, individual earthquakes do not necessarily affect sediment export at short timescales.

Needs and perspectives of odour research in the aquatic sciences

2007 ◽  
Vol 55 (5) ◽  
pp. 367-369
Author(s):  
F. Jüttner
Keyword(s):  
Secondary Metabolites ◽  
Food Web ◽  
Molecular Mechanisms ◽  
Temporal Distribution ◽  
Regulatory Mechanisms ◽  
Future Research ◽  
Spatial And Temporal Distribution ◽  
The Common ◽  
Aquatic Sciences

Over more than four decades odour research in the aquatic sciences has increasingly focused on cyanobacteria and the common odour-causing compounds, geosmin and 2-methylisoborneol. Success in future research requires a long-term perspective. Key areas for investigation are secondary metabolites and cyanobacteria, regulatory mechanisms for geosmin and other compounds' synthesis; understanding their spatial and temporal distribution (particularly relating to the food web in a habitat); and molecular mechanisms for liberation of geosmin by microorganisms.

Long-term trend analysis of deep-ocean acoustic noise data

2020 ◽  
Author(s):  
Sei-Him Cheong ◽  
Stephen P Robinson ◽  
Peter M Harris ◽  
Lian S Wang ◽  
Valerie Livina
Keyword(s):  
Trend Analysis ◽  
Sound Pressure ◽  
Functional Model ◽  
Deep Ocean ◽  
Ocean Noise ◽  
Noise Data ◽  
Long Term Trends ◽  
Long Term Trend ◽  
Monitoring Stations

&lt;p&gt;Underwater noise is recognised as a form of marine pollutant and there is evidence that over exposure to excessive levels of noise can have effects on the wellbeing of the marine ecosystem. Consequently, the variation in the ambient sound levels in the deep ocean has been the subject of a number of recent studies, with particular interest in the identification of long-term trends. We describe a statistical method for performing long-term trend analysis and uncertainty evaluation of the estimated trends from deep-ocean noise data. This study has been extended to include &amp;#160;measured data&amp;#160; from four monitoring stations located in the Indian (Cape Leeuwin &amp; Diego Garcia), Pacific (Wake Island) and Southern Atlantic (Ascension Islands) Oceans over periods spanning between 8 to 15 years. The data were obtained from the hydro-acoustic monitoring stations of the Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The monitoring stations provide information at a sampling frequency of 250 Hz, leading to very large datasets, and at acoustic frequencies up to 105 Hz.&lt;/p&gt;&lt;p&gt;The analysis method uses a flexible discrete model that incorporates terms that capture seasonal variations in the data together with a moving-average statistical model to describe the serial correlation of residual deviations. The trend analysis is applied to time series representing daily aggregated statistical levels for four frequency bands to obtain estimates for the change in sound pressure level (SPL) over the examined period with associated coverage intervals. The analysis demonstrates that there are statistically significant changes in the levels of deep-ocean noise over periods exceeding a decade. The main features of the approach include (a) using a functional model&amp;#160; with terms&amp;#160; that represent both long-term and seasonal behaviour of deep-ocean noise, (b) using a statistical model to capture the serial correlation of the residual deviations that are not explained by the functional model, (c) using daily aggregation intervals derived from 1-minute &amp;#160;sound pressure level averages, and (d) applying a non-parametric approach to validate the uncertainties of the trend estimates that avoids the need to make an assumption about the distribution of the residual deviations.&lt;/p&gt;&lt;p&gt;The obtained results show the long term trends vary differently at the four stations. It was observed that low frequency noise generally dominated the significant trends in these oceans. The relative differences between the various statistical levels are remarkably similar for all the frequency bands. Given the complexity of the acoustic environment, it is difficult to identify the main causes of these trends. Some possible explanations for the observed trends are discussed. It was however observed some stations are subjected to strong seasonal variation with a high degree of correlation with climatic factors such as sea surface temperature, Antarctic ice coverage and wind speed. The same seasonal effects is less pronounced in station located closer to the equator.&lt;/p&gt;

Spatial and temporal distribution of long-term short-wave surface radiation over Greece

2006 ◽  
Vol 132 (621) ◽  
pp. 2693-2718 ◽  
Author(s):  
A. Fotiadi ◽  
N. Hatzianastassiou ◽  
P. W. Stackhouse ◽  
C. Matsoukas ◽  
E. Drakakis ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Short Wave ◽  
Surface Radiation ◽  
Spatial And Temporal Distribution ◽  
Wave Surface

scholarly journals Long-Term Trends in 20-Day Cumulative Precipitation for Residential Rainwater Harvesting in Poland

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1932 ◽  
Author(s):  
Fausto A. Canales ◽  
Joanna Gwoździej-Mazur ◽  
Piotr Jadwiszczak ◽  
Joanna Struk-Sokołowska ◽  
Katarzyna Wartalska ◽  
...  
Keyword(s):  
Time Series ◽  
Water Conservation ◽  
Rainwater Harvesting ◽  
Kendall Test ◽  
Integrated Water Management ◽  
Operation Conditions ◽  
Long Time ◽  
Long Term Trends ◽  
Availability Index

Rainwater harvesting (RWH) for domestic uses is widely regarded as an economic and ecological solution in water conservation and storm management programs. This paper aims at evaluating long-term trends in 20-day cumulative rainfall periods per year in Poland, for assessing its impact on the design and operation conditions for RWH systems and resource availability. The time-series employed corresponds to a set of 50-year long time-series of rainfall (from 1970 to 2019) recorded at 19 synoptic meteorological stations scattered across Poland, one of the European countries with the lowest water availability index. The methods employed for assessing trends were the Mann–Kendall test (M–K) and the Sen’s slope estimator. Most of the datasets exhibit stationary behaviour during the 50-year long period, however, statistically significant downward trends were detected for precipitations in Wrocław and Opole. The findings of this study are valuable assets for integrated water management and sustainable planning in Poland.

scholarly journals Long-term patterns of spatial and temporal distribution in the seabob shrimp Xiphopenaeus kroyeri (Decapoda: Penaeidae) population in southeastern Brazil

2014 ◽  
Vol 34 (3) ◽  
pp. 326-333 ◽  
Author(s):  
Gisele Salgado Heckler ◽  
Roberto Munehisa Shimizu ◽  
Adilson Fransozo ◽  
Sergio Rosso ◽  
Rogerio Caetano da Costa
Keyword(s):  
Temporal Distribution ◽  
Southeastern Brazil ◽  
Spatial And Temporal Distribution ◽  
Xiphopenaeus Kroyeri

scholarly journals Homogenization and Trend Analysis of Canadian Near-Surface Wind Speeds

2010 ◽  
Vol 23 (5) ◽  
pp. 1209-1225 ◽  
Author(s):  
Hui Wan ◽  
Xiaolan L. Wang ◽  
Val R. Swail
Keyword(s):  
Wind Speed ◽  
Trend Analysis ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
The United States ◽  
Homogeneity Test ◽  
Near Surface ◽  
Wind Speeds ◽  
Long Term Trends

Abstract Near-surface wind speeds recorded at 117 stations in Canada for the period from 1953 to 2006 were analyzed in this study. First, metadata and a logarithmic wind profile were used to adjust hourly wind speeds measured at nonstandard anemometer heights to the standard 10-m level. Monthly mean near-surface wind speed series were then derived and subjected to a statistical homogeneity test, with homogeneous monthly mean geostrophic wind (geowind) speed series being used as reference series. Homogenized monthly mean near-surface wind speed series were obtained by adjusting all significant mean shifts, using the results of the statistical test and modeling along with all available metadata, and were used to assess the long-term trends. This study shows that station relocation and anemometer height change are the main causes for discontinuities in the near-surface wind speed series, followed by instrumentation problems or changes, and observing environment changes. It also shows that the effects of artificial mean shifts on the results of trend analysis are remarkable, and that the homogenized near-surface wind speed series show good spatial consistency of trends, which are in agreement with long-term trends estimated from independent datasets, such as surface winds in the United States and cyclone activity indices and ocean wave heights in the region. These indicate success in the homogenization of the wind data. During the period analyzed, the homogenized near-surface wind speed series show significant decreases throughout western Canada and most parts of southern Canada (except the Maritimes) in all seasons, with significant increases in the central Canadian Arctic in all seasons and in the Maritimes in spring and autumn.

Sign in / Sign up

Export Citation Format

Share Document