Mapping Erosion Prone Areas in the Bouhamdane Watershed (Algeria) Using the Revised Universal Soil Loss Equation Through GIS

DOI: 10.1515/jwld-2017-0002 © Polish Academy of Sciences (PAN), Committee on Agronomic Sciences JOURNAL OF WATER AND LAND DEVELOPMENT Section of Land Reclamation and Environmental Engineering in Agriculture, 2017 2017, No. 32 (I–III): 13–23 © Institute of Technology and Life Sciences (ITP), 2017 PL ISSN 1429–7426 Available (PDF): http://www.itp.edu.pl/wydawnictwo/journal; http://www.degruyter.com/view/j/jwld Received 10.09.2016 Mapping erosion prone areas Reviewed 20.10.2016 Accepted 03.11.2016 A – study design in the Bouhamdane watershed (Algeria) B – data collection C – statistical analysis D – data interpretation using the Revised Universal Soil Loss E – manuscript preparation F – literature search Equation through GIS Hamza BOUGUERRA1) BCDEF, Abderrazak BOUANANI1) ADF, Kamel KHANCHOUL2) ABC, Oussama DERDOUS3) DEF , Salah Eddine TACHI4) DE 1) University Abou Bakr Belkaid, Faculty of Technology, Department of Hydraulic, Laboratory No 25, BP 119 Tlemcen, 13000, Algeria; e-mail: [email protected]; [email protected] 2) University Badji Mokhtar, Faculty of Earth Sciences, Department of Geology, BP 12 Annaba, 23000, Algeria; e-mail: [email protected] 3) University Kasdi Merbah, Faculty of Applied Sciences, Department of civil engineering and hydraulic, Route Ghardaïa, BP 511, Ouargla, 30000, Algeria; e-mail: [email protected] 4) University Hassiba Ben Bouali Chlef, Laboratory of Water and Energy, Hay Salem National road Nr 19, Chlef 02000, Algeria; e-mail: [email protected] For citation: Bouguerra H., Bouanani A., Khanchoul K., Derdous O., Tachi S.E. 2017. Mapping erosion prone areas in the Bouhamdane watershed (Algeria) using the Revised Universal Soil Loss Equation through GIS. Journal of Water and Land Development. No. 32 p. 13–23. DOI: 10.1515/jwld-2017-0002 Abstract Soil erosion by water is a major problem that the Northern part of Algeria witnesses nowadays; it reduces: the productivity of agricultural areas due to the loss of lands, and leads to the loss of storage capacity in reser- voirs, the deterioration of water quality etc. The aim of this study is to evaluate the soil losses due to water erosion, and to identify the sectors which are potentially sensitive to water erosion in the Bouhamdane watershed, that is located in the northeastern part of Algeria. To this end, the Revised Universal Soil Loss Equation (RUSLE) was used. The application of this equation takes into account five parameters, namely the rainfall erosivity, topography, soil erodibility, vegetative cover and erosion control practices. The product of these parameters under GIS using the RUSLE mathematical equation has enabled evaluating an annual average erosion rate for the Bou- hamdane watershed of 11.18 t·ha–1·y–1. Based on the estimates of soil loss in each grid cell, a soil erosion risk map with five risk classes was elaborated. The spatial distribution of risk classes was 16% very low, 41% low, 28% moderate, 12% high and 3% very high. Most areas showing high and very high erosion risk occurred in the lower Bouhamdane watershed around Hammam Debagh dam. These areas require adequate erosion control practices to be implemented on a priority basis in order to conserve soil resources and reduce siltation in the reservoir. Key words: Algeria, Bouhamdane Watershed, GIS, Reservoir of Hammam Debagh, RUSLE, siltation, soil erosion INTRODUCTION water from raindrop, runoff, snowmelt, and irrigation. The raindrops affect the surface and go in the form of Water erosion is widespread phenomenon in the runoff which is the main factor of water erosion. Soil watersheds. It is the grignotage of the soil surface by erosion by water is a very widespread phenomenon in © Polish Academy of Sciences (PAN) in Warsaw, 2017; © Institute of Technology and Life Sciences (ITP) in Falenty, 2017 14 H. BOUGUERRA, A. BOUANANI, K. KHANCHOUL, O. DERDOUS, S.E. TACHI North Africa, especially in the Maghreb countries (Algeria, Tunisia and Morocco). The specific erosion rates exceed the tolerance thresholds in many areas in the northern part of the Maghreb region; DEMMAK [1982] observed an erosion rate of about 50 t·ha–1·y–1 at the Agrioum River northeastern Algeria. SAIDI [1991] states in his study that the specific erosion rates of the Fodda River (Chellif region) passed 20 –1 –1 t·ha ·y . BENBRAHIM et al. [2004] recorded in Mo- rocco, a soil degradation by water erosion of above 35 t·ha–1·y–1, at Telata River (Western Rif), Lebene River (Prerif) and Ourgha River (Prerif). In Algeria, the regularized volume in the 64 oper- ating large dams is getting reduced significantly due to the sediment discharge and its accumulation in res- ervoirs. According to the latest bathymetric surveys (2004–2005) conducted by the National Agency of Dams and Transfers; the loss of storage capacity rep- resents 13 % of the initial storage capacity. The Hammam Debagh Dam (Guelma Province) is amongst the dams seriously affected by siltation. This reservoir lost about 16 hm3 of storage capacity between 1988 and 2004. A situation that compelled us to study water erosion in the watershed feeding the Hammam Debagh dam. During the last 30 years the Revised Universal Soil Loss Equation (RUSLE) [RENARD et al. 1997; Fig. 1. Localization of the study area; WISCHMEIER, SMITH 1978] was applied widely by source: own elaboration hydrologist for predicting erosion risk in Africa [ADE- DIJI et al. 2010; ANGIMA et al. 2003; ANYS 1991; heterogeneous relief (Fig. 1) characterized by middle- ANYS et al. 1994; BENKADJA et al. 2015; BONN 1998; -class to steep slopes. CHEN et al. 2008; FAGBOHUN et al. 2016; LIGONJA, The study area is dominated by a Mediterranean SHRESTHA 2013; MATI, VEIHE 2001; MEDDI et al. climate, with a semiarid Southern part receiving an 2016; SMITH 1999]. In this paper, the RUSLE model average annual rainfall of 497 mm and a sub-humid was applied to quantify soil losses and to map erosion northern part where the average annual rainfall is prone areas in the Hammam Debagh watershed. about 618 mm·y–1, while the average annual tempera- The thematic layers that represent the implied ture recorded in Guelma meteorological station is factors in the RUSLE equation were developed and 17.85°C. Two periods can be distinguished; a rela- combined in Geographical Information System (GIS) tively cold and rainy period ranging from November environment. The results showed a very high annual to April with a minimum of 7.2°C recorded in Febru- degradation rate and identified high degradation areas ary and a hot and dry period from May to October that require urgent intervention in the Bouhamdane with a maximum degree of 29.7°C recorded in July. watershed. MATERIALS AND METHODS STUDY AREA The soil loss empirical model RUSLE [RENARD The Bouhamdane watershed, sub-basin of the et al. 1997] was used to assess the erosive potential in Seybouse watershed is located north-eastern Algeria the Bouhamdane watershed. The model was previ- between the longitude 6°47'02"and 7°14'44" E and ously proposed by WISCHMEIER and SMITH [1978] in between 36°30'28" and the latitude 36°07'49" N, 150 which soil loss in t·ha–1·y–1 is determined at a pixel km from the Algerian-Tunisian border (Fig. 1). scale. The map of soil loss is obtained as a product of The Bouhamdane River starts at Bordj Sabath in five factors: rainfall erosivity factor (R), topography the junction of Sabath and Zenati rivers; it is one of (LS), soil erodibility (K), cover-management (C) and the main tributaries of the Seybouse River. The water- support practice (P). shed has an area of 1056 km2 and a perimeter of 186 The RUSLE model has been integrated into km, which give it an elongated shape (Kc = 1.62). The a geographic information system (GIS). All thematic minimum altitude in the basin is 299 m, while the maps of factors affecting water erosion were devel- highest point is at the summit of Oum Settas Moun- oped on an existing database. The superposition of all tain at 1325 m. The watershed basin has a very rough physical and anthropogenic factors that control the © PAN in Warsaw, 2017; © ITP in Falenty, 2017; Journal of Water and Land Development. No. 32 (I–III) Mapping erosion prone areas in the Bouhamdane watershed (Algeria) using the Revised Universal Soil Loss Equation… 15 Fig. 2. Chart of the adopted methodology; source: own elaboration erosion phenomenon was conducted in raster mode from the average annual precipitation map of the based on the RUSLE mathematical equation: ANRH were digitized in GIS then interpolated throughout the entire watershed using Topo to Raster A = R·LS·K·C·P (1) interpolation tool (Fig. 3). The flowchart below (Fig. 2) summarizes all the According to the average annual precipitation in steps taken to quantify the average annual loss of soil the Bouhamdane watershed (Fig. 3), a strong North- and to assess the vulnerability of soil towards water South gradient is observed with a difference of about erosion throughout the Bouhamdane watershed. 300 mm between the highest and lowest precipita- tions. The GIS interpolation allowed estimating about R FACTOR 575 mm·y–1 as an average annual precipitation in the watershed. To calculate the annual rainfall erosivity factor in the Bouhamdane watershed, the empirical formula of HEUSCH [1971] developed in Morocco was chosen. This formula takes into account the average annual precipitation and the maximum precipitation in 24 hours on a 20 years return period. 2 R = 143⋅ log P P24 + 89,7 (2) ( 106 ) where: R = rainfall erosivity factor (MJ·mm·ha–1· –1 –1 h ·y ), P = average annual precipitation (mm); P24 = maximum precipitation in 24 hours of 20 years return period (mm).

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