Land use and climate change effects on water yield from East African forested water towers

Wamucii, Charles; Oel, Pieter van; Ligtenberg, A.; Gathenya, John Mwangi; Teuling, Adriaan J.

doi:10.5194/hess-25-5641-2021

Cited by 32 publications

(21 citation statements)

References 90 publications

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“…Africa boasts millions of low-order (first to third order) streams in the major water catchment areas in Eastern, Central, Southern and Western Africa. These streams often drain Afromontane humid regions that have high agricultural potential (Wamucii et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Low diversity of fishes in high elevation Afrotromontane streams renders them unsuitable for biomonitoring

2022

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Most of the rivers in the Afrotropics emerge from forested uplands that are prime for human activities, including crop farming, grazing and settlement. However, streams draining these areas have a low diversity of fishes, which limits their use as indicators of water quality and ecological status. Here, we developed macroinvertebrate-and fish-based indices of biotic integrity and evaluated their responses to human activities in the Sondu-Miriu River, Kenya. Overall, water quality declined downstream because of the cumulative effects of human activities. The upper reaches had poor fish diversity with at most three species, but macroinvertebrate communities were diverse on the entire gradient of the river. Metrics that have been used to develop indices of biotic integrity in the Lake Victoria basin were selected and evaluated for responsiveness to various forms of human disturbance along the river. The poor diversity of fishes in the upper reaches limited the number of metrics that could be developed and evaluated. The fish index was only successfully applied in the middle and lower reaches where fish diversity was high. However, macroinvertebrates were diverse and sensitive to human activities on the entire gradient of the river. This study shows that for biomonitoring, macroinvertebrate communities offer a better alternative to fishes in high elevation Afromontane streams that harbour poor fish assemblages.

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Section: Introductionmentioning

confidence: 99%

Low diversity of fishes in high elevation Afrotromontane streams renders them unsuitable for biomonitoring

2022

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“…Figure 3b further illustrates how these deviations from the predictive Budyko curve affect the estimation of water balances, despite that Budyko-simulated Q generally has a strong correlation (r=0.97) with observed Q, with an RMSE of 43.92 mm/yr. The overestimation of runoff in relatively drier catchments and underestimation of runoff in relatively wetter catchments by the Budyko framework were also reported by Wamucii, et al [4]. To further study the interannual variances of Budyko scatter, we also estimated the best-fit w for each catchment using a least square technique with annual time series of water balances, which is referred to as optimized w [40].…”

Section: Application Of the Extended Budyko Frameworkmentioning

confidence: 64%

“…The Budyko framework is a simple and powerful tool to parameterize precipitation partitioning at the mean annual scale, which estimates the evaporative index (EI) as an empirical curvilinear function of the climatic aridity index (AI) [2]. Based on studies around the world, Budyko-type equations were found to accurately estimate long-term water balance, which prompts a great deal of empirical-, theoretical-, and process-based studies [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Association of catchment characteristics to Budyko hydrologic model’s uncertainty in humid catchments

Zhang,

Marshall,

Vrieling

et al. 2023

Remote Sensing for Agriculture, Ecosystems, and Hydrology XXV

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Accurate quantification of precipitation partitioning into evapotranspiration and runoff is important for global water balance estimation and water resources managements. The Budyko framework is a simple yet robust solution to parameterize precipitation partitioning and has been widely applied for studying catchment-level water and energy fluxes. However, substantial variations between the observed and Budyko-predicted evaporative indices have been observed. Many studies have attributed the scatter around the Budyko curve to catchment characteristics (e.g., vegetation and soil property), which are not directly accounted for in the Budyko framework. However, modified Budyko-type equations that consider catchment characteristics are not transferable between regions and the interannual catchment behaviours still fail to follow the adjusted Budyko trajectories. To explore if the pronounced Budyko scatter in humid catchments has a systematic pattern caused by measurable catchment properties, this study comprehensively investigated the relationship between Budyko scatter and multiple catchment biophysical features from both spatial and temporal perspectives. Results reveal that for humid catchments, topography and seasonal cumulative moisture surplus can explain the spatial distributions of Budyko scatter with r higher than 0.65, whereas soil properties and vegetation indices explained little of the variance (r≤0.30). Temporally, the interannual variability of Budyko scatter was negatively correlated with annual average vegetation indices, particularly for catchments with relatively low vegetation cover. Overall, this study provides valuable insights to the interpretation of Budyko framework and offers possible solutions to improve its performance to predict the spatio-temporal variability of water balances.

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“…The above equation is valid under the assumption that basin storage changes can be neglected over long timescales (>10 years). A similar approach has been used to estimate annual runoff in several regions (e.g., Nkiaka et al, 2022; Wamucii et al, 2021; Zhang et al, 2023).…”

Section: Methodsmentioning

confidence: 99%

Changes in climate, vegetation cover and vegetation composition affect runoff generation in the Gulf of Guinea Basin

Nkiaka,

Okafor

2024

Hydrological Processes

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Although considerable effort has been deployed to understand the impact of climate variability and vegetation change on runoff in major basins across Africa, such studies are scarce in the Gulf of Guinea Basin (GGB). This study combines the Budyko framework and elasticity concept along with geospatial data to fill this research gap in 44 nested sub‐basins in the GGB. Annual rainfall from 1982 to 2021 show significant decreasing and increasing trends in the northern and southern parts of the GGB, respectively. Annual potential evapotranspiration (PET) also shows significant increasing trends with higher magnitudes observed in the northern parts of the GGB. Changing trends in climate variables corroborates with shift to arid and wetter conditions in the north and south, respectively. From 2000 to 2020 vegetation cover estimated using enhanced vegetation index (EVI) shows significant increasing trends in all sub‐basins including those experiencing a decline in annual rainfall. Vegetation composition measured using vegetation continuous fields (VCFs) from 2000 to 2020 show an increase in tree canopy cover (TC), a decline in short vegetation cover and marginal changes in bare ground cover (BG). Elasticity coefficients show that a 10% increase in annual rainfall and PET may lead to a 33% increase and 24% decline in runoff, respectively. On the other hand, a 10% increase in EVI may lead to a 4% decline in runoff while a 10% increase in TC, SV and BG may reduce runoff by 4% and increase runoff by 3% and 2%, respectively. Even though changes are marginal, decomposing vegetation into different parameters using EVI and VCFs may lead to different hydrological effects on runoff which is one of the novelties of this study that may be used for implementing nature‐based solutions. The study also demonstrates that freely available geospatial data together with analytical methods are a promising approach for understanding the impact of climate variability and vegetation change on hydrology in data‐scarce regions.

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Land use and climate change effects on water yield from East African forested water towers

Cited by 32 publications

References 90 publications

Low diversity of fishes in high elevation Afrotromontane streams renders them unsuitable for biomonitoring

Low diversity of fishes in high elevation Afrotromontane streams renders them unsuitable for biomonitoring

Association of catchment characteristics to Budyko hydrologic model’s uncertainty in humid catchments

Changes in climate, vegetation cover and vegetation composition affect runoff generation in the Gulf of Guinea Basin

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