Impact of the Sudd wetland on the Nile hydroclimatology

Mohamed, Yasir A.; Hurk, Bart van den; Savenije, Hubert; Bastiaanssen, W.G.M.

doi:10.1029/2004wr003792

Cited by 42 publications

(45 citation statements)

References 33 publications

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“…The lower panels show the difference in precipitation for JJA 1990-1999: e swamp − control, f swamp − bare desert soil the 95 % confidence level. Mohamed et al (2005b) find increases in the screen level temperature by 4 to 6°C during the dry season and 0.5 to 1°C during the wet season when the swamp region is drained, a result in line with those found here. Figure 10a, b also shows that the cooling effect by the swamp is mostly localized in nature.…”

Section: Impact On Rainfall and Ground Temperaturesupporting

confidence: 91%

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A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

Zaroug

Sylla

Giorgi

et al. 2012

Theor Appl Climatol

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We used the regional climate model RegCM3 to investigate the role of the swamps of southern Sudan in affecting the climate of the surrounding region. Towards this end, we first assessed the performance of a high resolution version of the model over northern Africa. RegCM3 shows a good skill in simulating the climatology of rainfall and temperature patterns as well as the related circulation features during the summer season, outperforming previous coarser resolution applications of the model over this region. Sensitivity experiments reveal that, relative to bare soil conditions, the swamps act to locally modify the surface energy budget primarily through an increase of surface latent heat flux. Existence of the swamps leads to lower ground temperature (up to 2°C), a larger north-south temperature gradient, and increased local rainfall (up to 40 %). Of particular importance is the impact on rainfall in the surrounding regions. The swamps have almost no impact on the rainfall over the source region of the Nile in Ethiopia or in the Sahel region; however, they favor wetter conditions over central Sudan (up to 15 %) in comparison to the bare desert soil conditions.

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Section: Impact On Rainfall and Ground Temperaturesupporting

confidence: 91%

“…Eltahir (1989) used a mathematical model to investigate soil-precipitation feedback mechanisms in annual rainfall over central Sudan, while Mohamed et al (2005b) used a regional climate model to study the impact of the Sudd wetland on the Nile basin.…”

Section: Introductionmentioning

confidence: 99%

A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

Zaroug

Sylla

Giorgi

et al. 2012

Theor Appl Climatol

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“…As for the Nile River basin, STEAM uses a static land-use map that does not include seasonal variations in wetland size or presence of reservoirs. Since the Nile contains the Sudd, one of the largest wetlands in the world with a highly variable size, evaporation simulation is challenging in this region, even in fineresolution models including complex processes (Mohamed, 2005;Mohamed et al, 2007). In several of the northern river basins (e.g.…”

Section: Runoffmentioning

confidence: 99%

Contrasting roles of interception and transpiration in the hydrological cycle – Part 1: Temporal characteristics over land

et al. 2014

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Abstract. Moisture recycling, the contribution of terrestrial evaporation to precipitation, has important implications for both water and land management. Although terrestrial evaporation consists of different fluxes (i.e. transpiration, vegetation interception, floor interception, soil moisture evaporation, and open-water evaporation), moisture recycling (terrestrial evaporation-precipitation feedback) studies have up to now only analysed their combined total. This paper constitutes the first of two companion papers that investigate the characteristics and roles of different evaporation fluxes for land-atmosphere interactions. Here, we investigate the temporal characteristics of partitioned evaporation on land and present STEAM (Simple Terrestrial Evaporation to Atmosphere Model) -a hydrological land-surface model developed to provide inputs to moisture tracking. STEAM estimates a mean global terrestrial evaporation of 73 900 km 3 year −1 , of which 59 % is transpiration. Despite a relatively simple model structure, validation shows that STEAM produces realistic evaporative partitioning and hydrological fluxes that compare well with other global estimates over different locations, seasons, and land-use types. Using STEAM output, we show that the terrestrial residence timescale of transpiration (days to months) has larger inter-seasonal variation and is substantially longer than that of interception (hours). Most transpiration occurs several hours or days after a rain event, whereas interception is immediate. In agreement with previous research, our simulations suggest that the vegetation's ability to transpire by retaining and accessing soil moisture at greater depth is critical for sustained evaporation during the dry season. We conclude that the differences in temporal characteristics between evaporation fluxes are substantial and reasonably can cause differences in moisture recycling, which is investigated more in the companion paper (van der Ent et al., 2014, hereafter Part 2).

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“…In general, the model provided a sound representation of the hydroclimatological processes over the region. The model has been run for a second scenario with the Sudd completely drained (Mohamed et al, 2005b). …”

Section: Regional Climate Modelingmentioning

confidence: 99%

“…Detailed analysis of the spatial variability of evaporation over the Sudd derived from remote sensing was discussed in Mohamed et al (2004). The regional climate modeling part and assessment of the Sudd's impact on the Nile hydroclimatology was discussed in Mohamed et al (2005a) and Mohamed et al (2005b). However, the main objective of this article is to present the piece-wise results published previously pertinent to the Sudd question into one paper, supported by new computations for 2 additional years.…”

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confidence: 99%

New lessons on the Sudd hydrology learned from remote sensing and climate modeling

Mohamed

Savenije

Bastiaanssen

et al. 2006

Hydrol. Earth Syst. Sci.

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Abstract. Despite its local and regional importance, hydrometeorological data on the Sudd (one of Africa's largest wetlands) is very scanty. This is due to the physical and political situation of this area of Sudan. The areal size of the wetland, the evaporation rate, and the influence on the micro and meso climate are still unresolved questions of the Sudd hydrology.The evaporation flux from the Sudd wetland has been estimated using thermal infrared remote sensing data and a parameterization of the surface energy balance (SEBAL model). It is concluded that the actual spatially averaged evaporation from the Sudd wetland over 3 years of different hydrometeorological characteristics varies between 1460 and 1935 mm/yr. This is substantially less than open water evaporation. The wetland area appears to be 70% larger than previously assumed when the Sudd was considered as an open water body. The temporal analysis of the Sudd evaporation demonstrated that the variation of the atmospheric demand in combination with the inter-annual fluctuation of the groundwater table results into a quasi-constant evaporation rate in the Sudd, while open water evaporation depicts a clear seasonal variability. The groundwater table characterizes a distinct seasonality, confirming that substantial parts of the Sudd are seasonal swamps.The new set of spatially distributed evaporation parameters from remote sensing form an important dataset for calibrating a regional climate model enclosing the Nile Basin. The Regional Atmospheric Climate Model (RACMO) provides an insight not only into the temporal evolution of the hydro-climatological parameters, but also into the land surface climate interactions and embedded feedbacks. The impact of the flooding of the Sudd on the Nile hydroclimatology has been analysed by simulating two land surface scenarios Correspondence to: Y. A. Mohamed (yasir1@unesco-ihe.org) (with and without the Sudd wetland). The paper presents some of the model results addressing the Sudd's influence on rainfall, evaporation and runoff of the river Nile, as well as the influence on the microclimate.The paper presents a case study that confirms the feasibility of using remote sensing data (with good spatial and poor temporal coverage) in conjunction with a regional climate model. The combined model provides good temporal and spatial representation in a region characterized by extremely scarce ground data.

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Impact of the Sudd wetland on the Nile hydroclimatology

Cited by 42 publications

References 33 publications

A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

Contrasting roles of interception and transpiration in the hydrological cycle – Part 1: Temporal characteristics over land

New lessons on the Sudd hydrology learned from remote sensing and climate modeling

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