scholarly journals Drivers of spatial and temporal variability of streamflow in the Incomati River basin

2015 ◽  
Vol 19 (2) ◽  
pp. 657-673 ◽  
Author(s):  
A. M. L. Saraiva Okello ◽  
I. Masih ◽  
S. Uhlenbrook ◽  
G. P. W. Jewitt ◽  
P. van der Zaag ◽  
...  
Keyword(s):  
Land Use ◽  
Statistical Analysis ◽  
Flow Regime ◽  
River Basin ◽  
Water Resource ◽  
Temporal Variability ◽  
Irrigated Agriculture ◽  
Spatial And Temporal Variability ◽  
Natural Flow Regime ◽  
Natural Flow

Abstract. The Incomati is a semi-arid trans-boundary river basin in southern Africa, with a high variability of streamflow and competing water demands from irrigated agriculture, energy, forestry and industries. These sectors compete with environmental flows and basic human water needs, resulting in a "stressed" water resource system. The impacts of these demands, relative to the natural flow regime, appear significant. However, despite being a relatively well-gauged basin in South Africa, the natural flow regime and its spatial and temporal variability are poorly understood and remain poorly described, resulting in a limited knowledge base for water resource planning and management decisions. Thus, there is an opportunity to improve water management, if it can be underpinned by a better scientific understanding of the drivers of streamflow availability and variability in the catchment. In this study, long-term rainfall and streamflow records were analysed. Statistical analysis, using annual anomalies, was conducted on 20 rainfall stations, for the period 1950–2011. The Spearman test was used to identify trends in the records on annual and monthly timescales. The variability of rainfall across the basin was confirmed to be high, both intra- and inter-annually. The statistical analysis of rainfall data revealed no significant trend of increase or decrease. Observed flow data from 33 gauges were screened and analysed, using the Indicators of Hydrologic Alteration (IHA) approach. Temporal variability was high, with the coefficient of variation of annual flows in the range of 1 to 3.6. Significant declining trends in October flows, and low flow indicators, were also identified at most gauging stations of the Komati and Crocodile sub-catchments; however, no trends were evident in the other parameters, including high flows. The trends were mapped using GIS and were compared with historical and current land use. These results suggest that land use and flow regulation are larger drivers of temporal changes in streamflow than climatic forces. Indeed, over the past 40 years, the areas under commercial forestry and irrigated agriculture have increased over 4 times.

scholarly journals Drivers of spatial and temporal variability of streamflow in the Incomati River Basin

2014 ◽  
Vol 11 (7) ◽  
pp. 8879-8921
Author(s):  
A. M. L. Saraiva Okello ◽  
I. Masih ◽  
S. Uhlenbrook ◽  
G. W. P. Jewitt ◽  
P. van der Zaag ◽  
...  
Keyword(s):  
Land Use ◽  
Statistical Analysis ◽  
Water Resources ◽  
Flow Regime ◽  
Temporal Variability ◽  
Irrigated Agriculture ◽  
Spatial And Temporal Variability ◽  
Natural Flow Regime ◽  
Natural Flow

Abstract. The Incomati is a semi-arid trans-boundary river basin in southern Africa, with a high variability of streamflow and competing water demands from irrigated agriculture, energy, forestry and industries. These sectors compete with environmental flows and basic human water needs, resulting in a "stressed" water resources system. The impacts of these demands, relative to the natural flow regime, appear significant. However, despite being a relatively well-gauged basin in South Africa, the natural flow regime and its spatial and temporal variability are poorly understood and remain poorly described, resulting in a limited knowledge base for water resources planning and management decisions. Thus, there is an opportunity to improve water management, if it can be underpinned by a better scientific understanding of the drivers of streamflow availability and variability in the catchment. In this study, long-term rainfall and streamflow records were analysed. Statistical analysis, using annual anomalies, was conducted on 20 rainfall stations, for the period of 1950 to 2011. The Spearman Test was used to identify any trends in the records at annual and monthly time scales. The variability of rainfall across the basin was confirmed to be high, both intra- and inter-annually. The statistical analysis of rainfall data revealed no significant trend of increase or decrease for the studied period. Observed flow data from 33 gauges was screened and analyzed, using the Indicators of Hydrologic Alteration (IHA) approach. Long-term analyses were conducted to identify temporal/spatial variability and trends in streamflow records. Temporal variability was high, with the coefficient of variation of annual flows in the range of 1 to 3.6. Significant declining trends in October flows, and low flows indicators were also identified at most gauging stations of the Komati and Crocodile sub-catchments, however no trends were evident on the other parameters, including high flows. The trends were mapped, using GIS and were compared to historical and current land use. These results suggest that land use and flow regulation are larger drivers of temporal changes in the streamflow than climatic forces. Indeed, over the past 40 years, the areas under commercial forestry and irrigated agriculture have increased over four times.

Assessment of the natural flow regime in a Mediterranean river impacted from irrigated agriculture

2016 ◽  
Vol 573 ◽  
pp. 1492-1502 ◽  
Author(s):  
Konstantinos Stefanidis ◽  
Yiannis Panagopoulos ◽  
Alexandros Psomas ◽  
Maria Mimikou
Keyword(s):  
Flow Regime ◽  
Irrigated Agriculture ◽  
Natural Flow Regime ◽  
Mediterranean River ◽  
Natural Flow

scholarly journals Natural flow regime, degree of alteration and environmental flows in the Mula stream (Segura River basin, SE Spain)

Limnetica ◽  
2010 ◽  
Vol 29 (2) ◽  
pp. 353-368
Author(s):  
Óscar Belmar ◽  
Josefa Velasco ◽  
Francisco Martínez-Capel ◽  
Antonio Alberto Marín
Keyword(s):  
Flow Regime ◽  
River Basin ◽  
Environmental Flows ◽  
Se Spain ◽  
Natural Flow Regime ◽  
Natural Flow

scholarly journals A hydrochemical modelling framework for combined assessment of spatial and temporal variability in stream chemistry: application to Plynlimon, Wales

2001 ◽  
Vol 5 (1) ◽  
pp. 49-58 ◽  
Author(s):  
H.J. Foster ◽  
M.J. Lees ◽  
H.S. Wheater ◽  
C. Neal ◽  
B. Reynolds
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Spatial Variability ◽  
Temporal Variability ◽  
Biological Diversity ◽  
Spatial And Temporal Variability ◽  
Stream Chemistry ◽  
Two Component ◽  
End Members

Abstract. Recent concern about the risk to biota from acidification in upland areas, due to air pollution and land-use change (such as the planting of coniferous forests), has generated a need to model catchment hydro-chemistry to assess environmental risk and define protection strategies. Previous approaches have tended to concentrate on quantifying either spatial variability at a regional scale or temporal variability at a given location. However, to protect biota from ‘acid episodes’, an assessment of both temporal and spatial variability of stream chemistry is required at a catchment scale. In addition, quantification of temporal variability needs to represent both episodic event response and long term variability caused by deposition and/or land-use change. Both spatial and temporal variability in streamwater chemistry are considered in a new modelling methodology based on application to the Plynlimon catchments, central Wales. A two-component End-Member Mixing Analysis (EMMA) is used whereby low and high flow chemistry are taken to represent ‘groundwater’ and ‘soil water’ end-members. The conventional EMMA method is extended to incorporate spatial variability in the two end-members across the catchments by quantifying the Acid Neutralisation Capacity (ANC) of each in terms of a statistical distribution. These are then input as stochastic variables to a two-component mixing model, thereby accounting for variability of ANC both spatially and temporally. The model is coupled to a long-term acidification model (MAGIC) to predict the evolution of the end members and, hence, the response to future scenarios. The results can be plotted as a function of time and space, which enables better assessment of the likely effects of pollution deposition or land-use changes in the future on the stream chemistry than current methods which use catchment average values. The model is also a useful basis for further research into linkage between hydrochemistry and intra-catchment biological diversity. Keywords: hydrochemistry, End-Member Mixing Analysis (EMMA), uplands, acidification

scholarly journals Impacts of Climate and Land-Use Change on Blue and Green Water: A Case Study of the Upper Ganjiang River Basin, China

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2661
Author(s):  
Yongfen Zhang ◽  
Chongjun Tang ◽  
Aizhong Ye ◽  
Taihui Zheng ◽  
Xiaofei Nie ◽  
...  
Keyword(s):  
Land Use ◽  
Resource Management ◽  
Water Resources ◽  
Land Use Change ◽  
River Basin ◽  
Water Resource ◽  
Water Resource Management ◽  
Green Water ◽  
Precipitation Changes ◽  
Ganjiang River Basin

Quantitatively figuring out the effects of climate and land-use change on water resources and their components is essential for water resource management. This study investigates the effects of climate and land-use change on blue and green water and their components in the upper Ganjiang River basin from the 1980s to the 2010s by comparing the simulated changes in blue and green water resources by using a Soil and Water Assessment Tool (SWAT) model forced by five climate and land-use scenarios. The results suggest that the blue water flow (BWF) decreased by 86.03 mm year−1, while green water flow (GWF) and green water storage (GWS) increased by 8.61 mm year−1 and 12.51 mm year−1, respectively. The spatial distribution of blue and green water was impacted by climate, wind direction, topography, and elevation. Climate change was the main factor affecting blue and green water resources in the basin; land-use change had strong effects only locally. Precipitation changes significantly amplified the BWF changes. The proportion of surface runoff in BWF was positively correlated with precipitation changes; lateral flow showed the opposite tendency. Higher temperatures resulted in increased GWF and decreased BWF, both of which were most sensitive to temperature increases up to 1 °C. All agricultural land and forestland conversion scenarios resulted in decreased BWF and increased GWF in the watershed. GWS was less affected by climate and land-use change than GWF and BWF, and the trends in GWS were not significant. The study provides a reference for blue and green water resource management in humid areas.

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