scholarly journals Interplay of riparian forest and groundwater in the hillslope hydrology of Sudanian West Africa (northern Benin)

2013 ◽  
Vol 17 (12) ◽  
pp. 5079-5096 ◽  
Author(s):  
A. Richard ◽  
S. Galle ◽  
M. Descloitres ◽  
J.-M. Cohard ◽  
J.-P. Vandervaere ◽  
...  
Keyword(s):  
West Africa ◽  
Transpiration Rate ◽  
Riparian Forest ◽  
Dry Season ◽  
Groundwater Table ◽  
Actual Evapotranspiration ◽  
Virtual Experiment ◽  
Deep Groundwater ◽  
Riparian Area ◽  
Study Results

Abstract. Forests are thought to play an important role in the regional dynamics of the West African monsoon, through their capacity to extract water from a permanent and deep groundwater table to the atmosphere even during the dry season. It should be the case for riparian forests too, as these streambank forests are key landscape elements in Sudanian West Africa. The interplay of riparian forest and groundwater in the local hydrodynamics was investigated, by quantifying their contribution to the water balance. Field observations from a comprehensively instrumented hillslope in northern Benin were used. Particular attention was paid to measurements of actual evapotranspiration, soil water and deep groundwater levels. A vertical 2-D hydrological modelling approach using the Hydrus software was used as a testing tool to understand the interactions between the riparian area and the groundwater. The model was calibrated and evaluated using a multi-criteria approach (reference simulation). A virtual experiment, including three other simulations, was designed (no forest, no groundwater, neither forest nor groundwater). The model correctly simulated the hydrodynamics of the hillslope regarding vadose zone dynamics, deep groundwater fluctuation and actual evapotranspiration dynamics. The virtual experiment showed that the riparian forest transpiration depleted the deep groundwater table level and disconnected it from the river, which is consistent with the observations. The riparian forest and the deep groundwater table actually form an interacting transpiration system: the high transpiration rate in the riparian area was shown to be due to the existence of the water table, supplied by downslope lateral water flows within the hillslope soil layer. The simulated riparian transpiration rate was practically steady all year long, around 7.6 mm d−1. This rate lies within high-end values of similar study results. The riparian forest as simulated here contributes to 37% of the annual hillslope transpiration, and reaches 57% in the dry season, whereas it only covers 5% of the hillslope area.

scholarly journals Riparian forest and permanent groundwater: a key coupling for balancing the hillslope water budget in Sudanian West Africa

2013 ◽  
Vol 10 (5) ◽  
pp. 5643-5686
Author(s):  
A. Richard ◽  
S. Galle ◽  
M. Descloitres ◽  
J. M. Cohard ◽  
J. P. Vandervaere ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Balance ◽  
Riparian Forest ◽  
Dry Season ◽  
Groundwater Table ◽  
Riparian Forests ◽  
Actual Evapotranspiration ◽  
Anthropogenic Pressure ◽  
Deep Groundwater ◽  
African Monsoon

Abstract. Forests are thought to play an important role in the regional dynamics of the West African monsoon, through their capacity to extract water from permanent aquifers located deep in the soil and pump it into the atmosphere even during the dry season. This is especially true for riparian forests located at the bottom of the hillslopes. This coupling between the riparian forests and the permanent aquifers is investigated, looking for quantifying its contribution to the catchment water balance. To this end, use is made of the observations available from a comprehensively instrumented hillslope through the framework of the AMMA-CATCH (African Monsoon Multidisciplinary Analysis – Coupling the Tropical Atmosphere and the Hydrological Cycle) observing system. Attention is paid to measurements of actual evapotranspiration, soil moisture and deep groundwater level. A vertical 2-D approach is followed using the physically-based Hydrus 2-D model in order to simulate the hillslope hydrodynamics, the model being calibrated and evaluated through a multi-criteria approach. The model correctly simulates the hydrodynamics of the hillslope as far as soil moisture dynamics, deep groundwater fluctuation and actual evapotranspiration dynamics are concerned. In particular, the model is able to reproduce the observed hydraulic disconnection between the deep permanent groundwater table and the river. A virtual experiment shows that the riparian forest depletes the deep groundwater table level through transpiration occurring throughout the year so that the permanent aquifer and the river are not connected. Moreover the riparian forest and the deep groundwater table form a coupled transpiration system: the riparian forest transpiration is due to the water redistribution at the hillslope scale feeding the deep groundwater through lateral saturated flow. The annual cycle of the transpiration origin is also quantified. The riparian forest which covers only 5% of the hillslope generates 37% of the annual transpiration, this proportion reaching 57% during the dry season. In a region of intense anthropogenic pressure, forest clearing and its replacement by cropping could impact significantly the water balance at catchment scale with a possible feedback on the regional monsoon dynamics.

STUDI BIONOMIK VEKTOR MALARIA DI KECAMATAN KALIBAWANG, KULONPROGO

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Sardjito Eko Windarso dkk
Keyword(s):  
Land Use ◽  
Malaria Vector ◽  
Rainy Season ◽  
Dry Season ◽  
Physical Factors ◽  
Mosquito Vector ◽  
Anopheles Species ◽  
Commercial Farming ◽  
Study Results ◽  
Dry And Rainy Seasons

The increasing of malaria cases in recent years at Kecamatan Kalibawang has been suspected correspond with the conversion of farming land-use which initiated in 1993. Four years after the natural vegetation in this area were changed become cocoa and coffee commercial farming estates, the number of malaria cases in 1997 rose more than six times, and in 2000 it reached 6085. This study were aimed to observe whether there were any differences in density and diversity of Anopheles as malaria vector between the cocoa and mix farming during dry and rainy seasons. The results of the study are useful for considering the appropriate methods, times and places for mosquito vector controlling. The study activities comprised of collecting Anopheles as well as identifying the species to determine the density and diversity of the malaria vector. Both activities were held four weeks in dry season and four weeks in rainy season. The mea-surement of physical factors such as temperature, humidity and rainfall were also conducted to support the study results. Four dusuns which meet the criteria and had the highest malaria cases were selected as study location. Descriptively, the results shows that the number of collected Anopheles in cocoa farming were higher compared with those in mix horticultural farming; and the number of Anopheles species identifi ed in cocoa farming were also more varied than those in the mix horticultural farming.Key words: bionomik vektor malaria, anopheles,

scholarly journals The Connection between Architectural Elements and Adaptive Thermal Comfort of Tropical Vernacular Houses in Mountain and Beach Locations

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7427
Author(s):  
Hermawan Hermawan ◽  
Jozef Švajlenka
Keyword(s):  
Thermal Comfort ◽  
Mixed Method ◽  
Rainy Season ◽  
Qualitative Methodology ◽  
Dry Season ◽  
Architectural Elements ◽  
Air Temperatures ◽  
Adaptive Thermal Comfort ◽  
Architectural Features ◽  
Study Results

Passive thermal comfort has been widely used to test the thermal performance of a building. The science of active thermal comfort is important to be connected with the science of architecture. The currently developing active thermal comfort is adaptive thermal comfort. Vernacular houses are believed to be able to create thermal comfort for the inhabitants. The present study seeks to analyze the connection between the architectural elements of vernacular houses and adaptive thermal comfort. A mixed method was applied. A quantitative approach was used in the measurement of variables of climate, while a qualitative methodology was employed in an interview on thermal sensations. The connection between architectural elements and adaptive thermal comfort was analyzed by considering the correlation among architectural features, the analysis results of thermal comfort, and the Olgyay and psychrometric diagrams. At the beginning of the rainy season, residents of exposed stone houses had the highest comfortable percentage of 31%. In the middle of the rainy season, the highest percentage of comfort was obtained by residents of exposed brick and wooden houses on the beach at 39%. The lowest comfortable percentage experienced by residents of exposed stone houses at the beginning of the dry season was 0%. The beginning of the dry season in mountainous areas has air temperatures that are too low, making residents uncomfortable. The study results demonstrate that adaptive thermal comfort is related to using a room for adaptation to create thermal comfort for the inhabitants.

scholarly journals How Some Trees Survive the Summer Dry Season

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Terri Cook
Keyword(s):  
Unsaturated Soil ◽  
Dry Season ◽  
Groundwater Table ◽  
Oak Trees

Oak trees in California seasonally tap moisture in unsaturated soil and weathered bedrock, even when the groundwater table is within reach of their roots.

scholarly journals Exploring the Major Climate-smart Agricultural Practices for Dry Season Crop Production in Salinity Affected Fallow Land in the Coastal Areas of Bangladesh

2021 ◽  
pp. 185-192
Author(s):  
Md. Abdul Awal
Keyword(s):  
Crop Production ◽  
Agricultural Practices ◽  
Conservation Agriculture ◽  
Safety Net ◽  
Coastal Areas ◽  
Dry Season ◽  
Fallow Land ◽  
Short Life Span ◽  
Crop Varieties ◽  
Study Results

The landmasses of the coastal areas of Bangladesh still remains under-utilized, thus cropping intensity is much less than the national average. Most areas remain fallow during dry (rabi) season from December to May due to presence of higher concentration of salts in soil and water, and scarcity of suitable irrigation water. Available adaptation options or technologies are not capable to solve these problems at all. Nevertheless, the areas receive a lot of water from monsoon rain, most of that rainwater is drain-out as surface runoff. The present study results suggest that the use of harvested rainwater and conservation agriculture either in combination or alone could mitigate the problem for bringing huge areas under crop cultivation. The public social safety net programmes such as cash-for-work, food-for-work etc. can be deployed for excavating or re-excavating the abandoned coastal ponds, ditches or canals for storing rainwater. Salt-, drought- and/or heat-tolerant crop varieties with short life span can also be cultivated to get the better results. Early plantation or growing crops with early-maturing varieties can ensure safer harvest in ahead of stress arrives. The avenues have immense potential as climate-smart practices for growing crops preferably non-rice crops during dry season in vast fallow land that will not only ensure food security for coastal people but could turn the entire southern Bangladesh as a food surplus zone. The findings refer the broad recommendation, therefore, specific research works based on the locations and resources available are necessary.

scholarly journals The impact of air–sea coupling and ocean biases on the seasonal cycle of southern West African precipitation

2019 ◽  
Vol 53 (11) ◽  
pp. 7027-7044
Author(s):  
Caroline M. Wainwright ◽  
Linda C. Hirons ◽  
Nicholas P. Klingaman ◽  
Richard P. Allan ◽  
Emily Black ◽  
...  
Keyword(s):  
West Africa ◽  
Atlantic Ocean ◽  
Crop Yields ◽  
Coupled Model ◽  
Dry Season ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Rainfall Regime ◽  
Climate Projections ◽  
The Impact

Abstract The biannual seasonal rainfall regime over the southern part of West Africa is characterised by two wet seasons, separated by the ‘Little Dry Season’ in July–August. Lower rainfall totals during this intervening dry season may be detrimental for crop yields over a region with a dense population that depends on agricultural output. Coupled Model Intercomparison Project Phase 5 (CMIP5) models do not correctly capture this seasonal regime, and instead generate a single wet season, peaking at the observed timing of the Little Dry Season. Hence, the realism of future climate projections over this region is questionable. Here, the representation of the Little Dry Season in coupled model simulations is investigated, to elucidate factors leading to this misrepresentation. The Global Ocean Mixed Layer configuration of the Met Office Unified Model is particularly useful for exploring this misrepresentation, as it enables separating the effects of coupled model ocean biases in different ocean basins while maintaining air–sea coupling. Atlantic Ocean SST biases cause the incorrect seasonal regime over southern West Africa. Upper level descent in August reduces ascent along the coastline, which is associated with the observed reduction in rainfall during the Little Dry Season. When coupled model Atlantic Ocean biases are introduced, ascent over the coastline is deeper and rainfall totals are higher during July–August. Hence, this study indicates detrimental impacts introduced by Atlantic Ocean biases, and highlights an area of model development required for production of meaningful climate change projections over the West Africa region.

scholarly journals Prediction of Dry-Season Precipitation in Tropical West Africa and Its Relation to Forcing from the Extratropics

2009 ◽  
Vol 24 (4) ◽  
pp. 1064-1084 ◽  
Author(s):  
Peter Knippertz ◽  
Andreas H. Fink
Keyword(s):  
West Africa ◽  
Local Population ◽  
Temporal Correlation ◽  
Global Precipitation Climatology Project ◽  
Precipitation Anomaly ◽  
Dry Season ◽  
Precipitation Event ◽  
Boreal Winter ◽  
False Alarms ◽  
Global Precipitation

Abstract Precipitation during the boreal winter dry season in tropical West Africa is rare but occasionally results in significant impacts on the local population. The dynamics and predictability of this phenomenon have been studied very little. Here, a statistical evaluation of the climatology, dynamics, and predictions of dry-season wet events is presented for the region 7.5°–15°N, 10°W–10°E. The analysis is based upon Global Precipitation Climatology Project (GPCP) merged satellite–gauge pentad rainfall estimates and 5-day 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) precipitation forecasts, and covers the 23 dry seasons (November–February) during 1979/80–2001/02. Wet events are defined as pentads with an area-averaged precipitation anomaly of more than +200% with respect to the mean seasonal cycle. Composites of the 43 identified events indicate an association with a trough over northwestern Africa, a tropical plume on its eastern side, unusual precipitation at the northern and western fringes of the Sahara, and reduced surface pressure over the Sahara, which allows an inflow of moist southerlies from the Gulf of Guinea to feed the unusual dry-season rainfalls. The results give evidence for a preconditioning by another disturbance about 1 week prior to the precipitation event. The ERA-40 forecasts show a high temporal correlation with observations, a general wet bias, but a somewhat too low number of wet events. With 53% of all identified events correctly forecasted and only 32% of forecasted events not verified, the model shows moderate skill in contrast to the prediction of many other tropical precipitation systems. A separate consideration of hits, misses, and false alarms corroborates the previously proposed hypothesis that a strong extratropical influence enhances the quality of predictions in this region. The results should encourage weather services in West Africa to take advantage of available dry-season precipitation forecasts in terms of the dissemination of early warnings.

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