scholarly journals Contributions of Human Activities and Climatic Variability to Changes in River Rwizi Flows in Uganda, East Africa

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 145
Author(s):  
Charles Onyutha ◽  
Resty Nyesigire ◽  
Anne Nakagiri
Keyword(s):  
Climate Variability ◽  
Human Activities ◽  
Large Scale ◽  
River Flow ◽  
Assessment Tool ◽  
Climatic Variability ◽  
Model Parameters ◽  
Catchment Management ◽  
Runoff Generation ◽  
Flow Changes

This study employed Soil and Water Assessment Tool (SWAT) to analyze the impacts of climate variability and human activities on River Rwizi flows. Changes in land use and land cover (LULC) types from 1997 to 2019 were characterized using remotely sensed images retrieved from Landsat ETM/TM satellites. SWAT was calibrated and validated over the periods 2002–2008 and 2009–2013, respectively. Correlation between rainfall and river flow was analyzed. By keeping the optimal values of model parameters fixed while varying the LULC maps, differences in the modeled flows were taken to reflect the impacts of LULC changes on rainfall–runoff generation. Impacts due to human activities included contributions from changes in LULC types and the rates of water abstracted from the river as a percentage of the observed flow. Climate variability was considered in terms of changes in climatic variables such as rainfall and evapotranspiration, among others. Variability of rainfall was analyzed with respect to changes in large-scale ocean-atmosphere conditions. From 2000 to 2014, the portion of River Rwizi catchment area covered by cropland increased from 23.0% to 51.6%, grassland reduced from 63.3% to 37.8%, and wetland decreased from 8.1% to 4.7%. Nash–Sutcliffe Efficiency values for calibration and validation were 0.60 and 0.71, respectively. Contributions of human activities to monthly river flow changes varied from 2.3% to 23.5%. Impacts of human activities on the river flow were on average found to be larger during the dry (14.7%) than wet (5.8%) season. Using rainfall, 20.9% of the total river flow variance was explained. However, climate variability contributed 73% of the river flow changes. Rainfall was positively and negatively correlated with Indian Ocean Dipole (IOD) and Niño 3, respectively. The largest percentages of the total rainfall variance explained by IOD and Niño 3 were 12.7% and 9.8%, respectively. The magnitude of the correlation between rainfall and IOD decreased with increasing lag in time. These findings are relevant for developing River Rwizi catchment management plans.

scholarly journals Spatio-temporal modeling of surface runoff in ungauged sub-catchments of Subarnarekha river basin using SWAT

MAUSAM ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 597-606
Author(s):  
CHINMAYA PANDA ◽  
DWARIKA MOHAN DAS ◽  
B. C. SAHOO ◽  
B. PANIGRAHI ◽  
K. K. SINGH
Keyword(s):  
Surface Runoff ◽  
Assessment Tool ◽  
Nutrient Loss ◽  
Coefficient Of Determination ◽  
Annual Rainfall ◽  
Model Parameters ◽  
Runoff Generation ◽  
Temporal Modeling ◽  
Spatio Temporal ◽  
R Factors

In this present study, Soil and Water Assessment Tool (SWAT) embedded with ArcGIS interface has been used to simulate the surface runoff from the un-gauged sub-catchments in the upper catchment of Subarnarekha basin. Model calibration and validation were performed with the help of Sequential Uncertainty Fitting (SUFI-2) in-built in the SWAT-CUP package (SWAT Calibration Uncertainty Programs). The model was calibrated for a period from 1996 to 2008 with 3 years warm up period (1996-1998) and validated for a period of 5 years from 2009 to 2013. The model evaluation was performed by Nash - Sutcliffe coefficient (NSE), Coefficient of determination (R2) and Percentage Bias (PBIAS). The degree of uncertainty was evaluated by P and R factors. Basing upon the R2, NSE and PBIAS values respectively, of the order of 0.90, 0.90 and -12%, during calibration and 0.85, 0.83 and -15% during validation, substantiate performance of the model. All uncertainties of model parameters have been well taken by the P and R factors respectively, of the order of 0.95 and 0.77 during calibration and 0.82 and 0.87 during validation. The runoff generation from 19 sub-catchments of Adityapur catchment varies from 29.2-44.1% of the annual rainfall and average surface runoff simulated for the entire catchment is 545 mm. As the surface runoff generated in most of the sub-catchments amounts to above 30% of rainfall, it is recommended for adequate number of structural interventions at appropriate locations in the catchment to store the rainfall excess for providing irrigation, recharging groundwater and restricting the sediment and nutrient loss.

scholarly journals Synchronous combined effects of fishing and climate within a demersal community

2012 ◽  
Vol 70 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Antoni Quetglas ◽  
Francesc Ordines ◽  
Manuel Hidalgo ◽  
Sebastià Monserrat ◽  
Susana Ruiz ◽  
...  
Keyword(s):  
Climate Variability ◽  
Age Structure ◽  
Large Scale ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Early Period ◽  
Combined Effects ◽  
Population Fluctuations ◽  
Fishing Activity ◽  
The Mediterranean

Abstract Quetglas, A., Ordines, F., Hidalgo, M., Monserrat, S., Ruiz, S., Amores, Á., Moranta, J., and Massutí, E. 2013. Synchronous combined effects of fishing and climate within a demersal community. – ICES Journal of Marine Science, 70: 319–328. Accumulating evidence shows that fishing exploitation and environmental variables can synergistically affect the population dynamics of exploited populations. Here, we document an interaction between fishing impact and climate variability that triggered a synchronic response in the population fluctuations of six exploited species in the Mediterranean from 1965–2008. Throughout this period, the fishing activity experienced a sharp increase in fishing effort, which caused all stocks to shift from an early period of underexploitation to a later period of overexploitation. This change altered the population resilience of the stocks and brought about an increase in the sensitivity of its dynamics to climate variability. Landings increased exponentially when underexploited but displayed an oscillatory behaviour once overexploited. Climatic indices, related to the Mediterranean mesoscale hydrography and large-scale north Atlantic climatic variability, seemed to affect the species with broader age structure and longer lifespan, while the global-scale El Niño Southern Oscillation index (ENSO) positively influenced the population abundances of species with a narrow age structure and short lifespan. The species affected by ENSO preferentially inhabit the continental shelf, suggesting that Mediterranean shelf ecosystems are sensitive to the hydroclimatic variability linked to global climate.

scholarly journals Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

2018 ◽  
Author(s):  
Rashid Mahmood ◽  
Shaofeng Jia
Keyword(s):  
Climate Variability ◽  
Human Activities ◽  
Climatic Variability ◽  
Change Point Analysis ◽  
Lake Chad ◽  
Average Decrease ◽  
The North ◽  
Sustainable Water Resources Management ◽  
Point Analysis ◽  
The 1960S

Abstract. In the 1960s, Lake Chad was the world’s sixth largest water body, which has since shrunk dramatically from a surface area of 25,000 km2 to only 2,000 km2 in the following 40 years. In the present study, hydro-climatic variability in the Chari-Logone, Komadugu-Yobe, YENG (Yedseram, El-Beid, Ngadda and Gubio basins) as well as Lake Fitri basins and decreasing streamflow to Lake Chad due to climate variability and human activities were separated and quantified using trend analysis, change point analysis, and hydrological approach, for the period of 1951–2015. The results showed very strong signals (α = 0.001) of increasing trend in mean temperature, with an average increase of 1.4 °C, and very weak (α = 0.1) to strong (α = 0.01) decreasing signals in precipitation, with an average decrease of 15 %. In case of streamflow to Lake Chad, very strong decreasing trends were observed, showing 67 % reduction for the whole period. The north-eastern parts were most affected parts in case of increasing temperature and decreasing precipitation. Decreasing flow due to both climate variability and human activities were ranged from 34 % to 45 % in different decades, from 1972 to 2013. On the whole, a 66 % of total decline in streamflow was observed due to human activities and 34 % due to climate variability. Most reduction in streamflow (59 %) due to climate variability was explored only during 1982–1991 because a devastating drought was occurred during this period. Since human activities caused most reduction in streamflow to Lake Chad than climate, inflow to the lake can be improved by reducing or properly managing the human activities and using sustainable water resources management.

scholarly journals SWAT-Simulated Streamflow Responses to Climate Variability and Human Activities in the Miyun Reservoir Basin by Considering Streamflow Components

2018 ◽  
Vol 10 (4) ◽  
pp. 941 ◽  
Author(s):  
Tiezhu Yan ◽  
Jianwen Bai ◽  
Amelia LEE ZHI YI ◽  
Zhenyao Shen
Keyword(s):  
Water Resources ◽  
Climate Variability ◽  
Water Resources Management ◽  
Human Activities ◽  
Assessment Tool ◽  
Drinking Water Source ◽  
Miyun Reservoir ◽  
Beijing City ◽  
Resources Management ◽  
Reservoir Basin

The streamflow into Miyun Reservoir, the only surface drinking water source for Beijing City, has declined dramatically over the past five decades. Thus, the impacts of climate variability and human activities (direct and indirect human activities) on streamflow and its components (baseflow and quickflow) needs to be quantitatively estimated for the sustainability of regional water resources management. Based on a heuristic segmentation algorithm, the chosen study period (1969–2012) was segmented into three subseries: a baseline period (1969–1979) and two impact periods I (1980–1998) and II (1999–2012). The Soil and Water Assessment Tool (SWAT) was adopted to investigate the attributions for streamflow change. Our results indicated that the baseflow accounted for almost 63.5% of the annual streamflow based on baseflow separation. The contributions of climate variability and human activities to streamflow decrease varied with different stages. During impact period I, human activities was accountable for 54.3% of the streamflow decrease. In impact period II, climate variability was responsible for 64.9%, and about 8.3 mm of baseflow was extracted from the stream on average based on the comparison of the observed streamflow and simulated baseflow. The results in this study could provide necessary information for water resources management in the watershed.

Spatial–Temporal Changes of Water Resources in a Typical Semiarid Basin of North China over the Past 50 Years and Assessment of Possible Natural and Socioeconomic Causes

2013 ◽  
Vol 14 (4) ◽  
pp. 1009-1034 ◽  
Author(s):  
Bin Yong ◽  
Liliang Ren ◽  
Yang Hong ◽  
Jonathan J. Gourley ◽  
Xi Chen ◽  
...  
Keyword(s):  
Water Resources ◽  
Climate Variability ◽  
Human Activities ◽  
Large Scale ◽  
Management Strategies ◽  
Annual Streamflow ◽  
Infiltration Capacity ◽  
Water Shortages ◽  
The Past ◽  
Runoff Reduction

Abstract Hydrological processes in most semiarid regions on Earth have been changing under the impacts of climate change, human activities, or combinations of the two. This paper first presents a trend analysis of the spatiotemporal changes in water resources and then diagnoses their underlying atmospheric and socioeconomic causes over 10 catchments in the Laoha basin, a typical semiarid zone of northeast China. The impacts of climate variability and human activities on streamflow change were quantitatively evaluated by the VIC (Variable Infiltration Capacity) model. First, results indicate that six out of the 10 studied catchments have statistically significant downward trends in annual streamflow; however, there is no significant change of annual precipitation for all catchments. Two abrupt changes of annual streamflow at 1979 and 1998 are identified for the four largest catchments. Second, the Laoha basin generally experienced three evident dry–wet pattern switches during the past 50 years. Furthermore, this basin is currently suffering from unprecedented water shortages. Large-scale climate variability has affected the local natural hydrologic system. Third, quantitative evaluation shows human activities were the main driving factors for the streamflow reduction with contributions of approximately 90% for the whole basin. A significant increase in irrigated area, which inevitably resulted in tremendous agricultural water consumption, is the foremost culprit contributing to the dramatic runoff reduction, especially at midstream and downstream of the Laoha basin. This study is expected to enable policymakers and stakeholders to make well-informed, short-term practice decisions and better plan long-term water resource and ecoenvironment management strategies.

Variability and Predictability of Central Asia River Flows: Antecedent Winter Precipitation and Large-Scale Teleconnections

2008 ◽  
Vol 9 (6) ◽  
pp. 1334-1349 ◽  
Author(s):  
Mathew A. Barlow ◽  
Michael K. Tippett
Keyword(s):  
Climate Variability ◽  
Central Asia ◽  
Moisture Transport ◽  
Large Scale ◽  
River Flow ◽  
Regional Scale ◽  
Warm Season ◽  
Cold Season ◽  
River Flows ◽  
Syr Darya

Abstract Warm season river flows in central Asia, which play an important role in local water resources and agriculture, are shown to be closely related to the regional-scale climate variability of the preceding cold season. The peak river flows occur in the warm season (April–August) and are highly correlated with the regional patterns of precipitation, moisture transport, and jet-level winds of the preceding cold season (November–March), demonstrating the importance of regional-scale variability in determining the snowpack that eventually drives the rivers. This regional variability is, in turn, strongly linked to large-scale climate variability and tropical sea surface temperatures (SSTs), with the circulation anomalies influencing precipitation through changes in moisture transport. The leading pattern of regional climate variability, as resolved in the operationally updated NCEP–NCAR reanalysis, can be used to make a skillful seasonal forecast for individual river flow stations. This ability to make predictions based on regional-scale climate data is of particular use in this data-sparse area of the world. The river flow is considered in terms of 24 stations in Uzbekistan and Tajikistan available for 1950–85, with two additional stations available for 1958–2003. These stations encompass the headwaters of the Amu Darya and Syr Darya, two of the main rivers of central Asia and the primary feeders of the catastrophically shrinking Aral Sea. Canonical correlation analysis (CCA) is used to forecast April–August flows based on the period 1950–85; cross-validated correlations exceed 0.5 for 10 of the stations, with a maximum of 0.71. Skill remains high even after 1985 for two stations withheld from the CCA: the correlation for 1986–2002 for the Syr Darya at Chinaz is 0.71, and the correlation for the Amu Darya at Kerki is 0.77. The forecast is also correlated to the normalized difference vegetation index (NDVI); maximum values exceed 0.8 at 8-km resolution, confirming the strong connection between hydrology and growing season vegetation in the region and further validating the forecast methodology.

scholarly journals Contribution of climatic variability and human activities to stream flow changes in the Haraz River basin, northern Iran

2019 ◽  
Vol 25 ◽  
pp. 12-24 ◽  
Author(s):  
Abdollah Pirnia ◽  
Hamid Darabi ◽  
Bahram Choubin ◽  
Ebrahim Omidvar ◽  
Charles Onyutha ◽  
...  
Keyword(s):  
River Basin ◽  
Human Activities ◽  
Stream Flow ◽  
Climatic Variability ◽  
Northern Iran ◽  
Haraz River ◽  
Flow Changes

scholarly journals Identifying dominant component of runoff yield processes: a case study in a sub-basin of the middle Yellow River

2021 ◽  
Author(s):  
Li Zhang ◽  
Caihong Hu ◽  
Shengqi Jian ◽  
Qiang Wu ◽  
Guang Ran ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Conservation ◽  
Human Activities ◽  
Large Scale ◽  
Overland Flow ◽  
Yellow River ◽  
Potential Evapotranspiration ◽  
Subsurface Flow ◽  
Runoff Generation ◽  
Runoff Reduction

Abstract The effects of long-term natural climate change and human activities on runoff generation mechanism in the middle Yellow River Basin are long-standing concerns. This study analyzed the characteristics of hydro-climatic variables in the meso-scale Tuweihe catchment based on the observed data for the period 1956–2016 and a climate elastic method. The spatial distribution of dominant runoff processes (DRP) following land use changes in case of rainfall was identified. The results show significant decreasing trends in annual runoff, whereas slightly downward trends are identified for annual precipitation and potential evapotranspiration, 1984 is detected as the mutation year of the study period. The average contributions of climate change and human activities to the runoff reduction in the Tuweihe catchment were 33.2% and 66.8%, respectively. In general, the influences of human activities on runoff are applied mostly through the alteration of the catchment characteristics. The dominant runoff processes changes between 1980 and 2015 show significant effects of large-scale soil and water conservation measures in the Tuweihe catchment. We found that Hortonian overland flow (HOF) and fast subsurface flow (SSF1) were the two main processes in 1980 (30.3% and 34.4% respectively), but the proportion of HOF decreased by 9.6% in 2015. The proportions of saturation overland flow (SOF) and SSF have increased to varying degrees, which means that the catchment is more prone to generate subsurface flow processes. Consequently, under similar rainfall conditions, the runoff yield of flood events decreases in the second period.

Assessing the impacts of climate variability and human activities on annual runoff in the Luan River basin, China

2013 ◽  
Vol 44 (5) ◽  
pp. 940-952 ◽  
Author(s):  
Xiangyu Xu ◽  
Hanbo Yang ◽  
Dawen Yang ◽  
Huan Ma
Keyword(s):  
Climate Variability ◽  
Human Activities ◽  
Large Scale ◽  
Vegetation Change ◽  
Hydrological Model ◽  
Climate Impact ◽  
Annual Runoff ◽  
Climate Elasticity ◽  
Antecedent Precipitation ◽  
Runoff Change

Regional hydrological processes have been greatly influenced by human activities and climate variability. The inflow of Panjiakou Reservoir, which is the largest reservoir located on the Luan River, has shown a significant decreasing trend over the past 50 years. A large-scale hydrological model, namely the geomorphology-based hydrological model (GBHM), and a climate elasticity model were applied to perform quantitative attributing analysis of runoff change in the study catchment. Annual runoff decreased by 19.5 mm from 65.7 mm in the period 1956–1979 to 46.2 mm in the period 1980–2005. Annual direct water intake increased by 22.5 mm from 3.6 to 26.1 mm. Climate impact was accountable for the runoff increase of 8.8 and 9.2 mm simulated by GBHM and the climate elasticity model, respectively. Impacts of land use and vegetation change accounted for the runoff decrease of 2.5 mm. Change of precipitation and vegetation cover contributed to annual runoff change for the upper catchment (grassland-dominated). Change of antecedent precipitation (a proxy of soil moisture) also contributed to annual runoff change for the lower catchment (forest-dominated) and the whole catchment (mixture vegetation).

A large-scale hydroclimatological perspective on western European river flow regimes

2012 ◽  
Vol 44 (5) ◽  
pp. 809-833 ◽  
Author(s):  
Donna Wilson ◽  
David M. Hannah ◽  
Glenn R. McGregor
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
River Flow ◽  
Flow Regimes ◽  
Climatic Conditions ◽  
Low Flow ◽  
Annual Rainfall ◽  
Time Variability ◽  
Runoff Generation

A novel flow regime classification scheme was applied to 141 river basins across western Europe, providing more robust analysis of space–time variability in regimes and their driving hydroclimatological processes. Regime shape (timing) and magnitude (size) were classified to regionalise long-term average flow regimes and to quantify year-to-year variation in regimes for each basin. Six long-term regime shape regions identified differences in seasonality related to latitude and altitude. Five long-term magnitude regions were linked to location plus average annual rainfall. Spatial distribution of long-term regimes reflected dominant climate and runoff generation processes. Regions were used to structure analysis of (relative) inter-annual regime dynamics. Six shape and five magnitude inter-annual regimes were identified; and regime stability (switching) assessed at pan-European, regional and basin scales. In some years, certain regime types were more prevalent, but never totally dominant. Regime shape was more stable at higher altitude due to buffering by frozen water storage-release (cf. more variable rainfall-runoff at lower altitudes). The lower inter-annual magnitude regimes persisted across larger domains (cf. higher magnitude) due to the more widespread climatic conditions generating low flow. Notably, there was limited spatio-temporal correspondence between regime shape and magnitude, suggesting variations in one attribute cannot be used to infer the other.

Sign in / Sign up

Export Citation Format

Share Document