scholarly journals Integrating Sediment (dis)Connectivity into a Sediment Yield Model for Semi-Arid Catchments

Land ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1204
Author(s):  
Louise Lodenkemper ◽  
Kate Rowntree ◽  
Denis Hughes ◽  
Andrew Slaughter

Soil erosion-associated sedimentation has become a significant global threat to sustainable land and water resources management. Semi-arid regions that characterise much of southern Africa are particularly at risk due to extreme hydrological regimes and sparse vegetative cover. This study aims to address the need for an erosion and sediment delivery model that successfully incorporates our conceptual understanding of sedimentation processes in semi-arid regions, particularly sediment storage and connectivity within a catchment. Priorities of the Semi-arid Sediment Yield Model (SASYM) were simplicity and practical applicability for land and water resource management while adhering to basic geomorphic and hydrological principles. SASYM was able to represent multiple sediment storages within a catchment to effectively represent a change in landscape connectivity over geomorphic timeframes. SASYM used the Pitman rainfall–runoff model disaggregated to a daily timescale, the Modified Universal Soil Loss Equation (MUSLE), incorporating probability function theory and a representation of sediment storages and connectors across a semi-distributed catchment. SASYM was applied to a catchment in the Karoo, South Africa. Although there were limited observed data, there was a historical dataset available for the catchment through dam sedimentation history. SASYM was able to effectively present this history and provide evidence for landscape connectivity change.

1987 ◽  
Vol 19 (9) ◽  
pp. 97-106
Author(s):  
J. J. Vasconcelos

Hater resource managers in semi-arid regions are faced with some unique problems. The wide variations in precipitation and stream flows in semi-arid regions increase man's dependence on the ground water resource for an ample and reliable supply of water. Proper management of the ground water resource is absolutely essential to the economic well being of semi-arid regions. Historians have discovered the remains of vanished advanced civilizations based on irrigated agriculture which were ignorant of the importance of proper ground water resource management. In the United States a great deal of effort is presently being expended in the study and control of toxic discharges to the ground water resource. What many public policy makers fail to understand is that the potential loss to society resulting from the mineralization of the ground water resource is potentially much greater than the loss caused by toxic wastes discharges, particularly in developing countries. Appropriations for ground water resource management studies in developed countries such as the United States are presently much less than those for toxic wastes management and should be increased. It is the reponsibility of the water resource professional to emphasize to public policy makers the importance of ground water resource management. Applications of ground water resource management models in the semi-arid Central Valley of California are presented. The results demonstrate the need for proper ground water resource management practices in semi-arid regions and the use of ground water management models as a valuable tool for the water resource manager.


1945 ◽  
Vol 82 (1) ◽  
pp. 16-18 ◽  
Author(s):  
H. L. Richardson

With regard to the relation between climatic oscillation and terrace formation, some ideas that I have collected in the course of studying accelerated (man-made) erosion, may be useful in a geo-morphological setting. Huntington’s principle and the idea I used in my paper “The Ice Age in West China” are not necessarily opposed, if one limits the application of Huntington’s principle to semi-arid regions which are just on the margin of being able to support a vegetative cover. In such regions a further decrease in precipitation, leading to serious reduction in the protection afforded by vegetation, would accelerate erosion on hillsides and steep valley floors, and this in turn would lead to deposition of spoil on more gently sloping valley floors lower down. A further oscillation of the climate, in the direction of increasing rainfall, would restore the vegetative cover, reduce erosion, reduce the load in the rivers, and allow downcutting to continue. But a still further increase in precipitation might be expected to increase erosion of the type associated with landslips and flooded streams and rivers; once more increased load will be swept down from the steeper hills and stream-beds to the lower and gentler slopes of the rivers, where it will be deposited. In other words, one may say that there is a level of precipitation, probably a moderately low one, at which (apart from human interference) there is a close vegetative cover and geological erosion is at a minimum; any appreciable departure from this level of precipitation in either direction will cause increased geological erosion in the upper courses of streams, and hence increased deposition in their lower courses.


1939 ◽  
Vol 76 (9) ◽  
pp. 402-407
Author(s):  
C. A. Cotton

It is difficult to draw the line between aridity and semi-aridity, just as it-is difficult to differentiate between humid and semi-arid climates as they affect the development of landscape forms. No hard and fast divisions based on rainfall figures can be adopted. Evaporation, in part controlled by temperature, and the seasonal distribution of rainfall are also important factors. “The rainfall regime is divisible”, according to. Bryan, “into the episodic and the periodic. In the episodic type rain falls in storms that are highly variable in intensity and are scattered through the year; in the periodic type precipitation is concentrated in one season, either summer or winter. In areas having the periodic type vegetation is adjusted to the wet season, and a relatively greater vegetative cover is possible with low rainfall. The Mediterranean region and California have the periodic type of rainfall, with winter maximum and mild temperatures. Thus in many sub-areas the land forms under mean annual rainfalls of 15 to 20 inches are very similar to those of humid regions, although the soils … are quite like those of other arid regions. The episodic rainfall, because of its variability in time throughout the year, is less effective in promoting growth, and the vegetative cover may be so scant with rainfalls of 5 to 7 inches that geomorphologically the region is essentially a desert. Episodic rainfall as high as 15 to 20 inches may produce steppe conditions. … In general the warmer areas have a relatively scantier vegetation with the same rainfall regime. Including this relation all varieties of hot and cold deserts or semi-arid climates are possible (2).”


RBRH ◽  
2020 ◽  
Vol 25 ◽  
Author(s):  
José Almir Cirilo ◽  
Lívia Fragoso de Melo Verçosa ◽  
Mayara Maria de Arruda Gomes ◽  
Maria Alice Britto Feitoza ◽  
Gadadhara de Figueiredo Ferraz ◽  
...  

ABSTRACT Despite the advances undertaken in recent years, modeling watershed’s hydrological responses remains a complex task, especially in data-scarce areas. In order to overcome this, new models with distinct representations of hydrological processes continue to be developed, incorporating spatial data and geoprocessing tools. In this article, the CAWM IV (Campus Agreste Watershed Model Version IV) model is presented. It is a conceptual model developed with the purpose of contributing mainly to the hydrological modeling of basins inserted in semi-arid regions. The article provides the layout of the mathematical model structure and a set of results obtained from the application of the model to basins with different characteristics. The main features of the model are the reduced number of parameters to calibrate and the incorporation of the basin physical characteristics in the calculation of several attributes, in order to facilitate the process of regionalization for other similar basins, particularly due to the absence of flow data. The CAWM IV model was applied to four basins located in the state of Pernambuco, in the Northeast region of Brazil. The model presented adequate behavior for 55 to 92% of the simulated events, depending on the criteria of performance indicators used in the analysis.


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