Hydrologic Modeling Using SWAT: Test the Capacity of SWAT Model to Simulate the Hydrological Behavior of Watershed in Semi-Arid Climate

Hydrologic Modeling Using SWAT: Test the Capacity of SWAT Model to Simulate the Hydrological Behavior of Watershed in Semi-Arid Climate

Zineb Moumen (University of Sidi Mohamed Ben Abdellah of Fez, Morocco), Soumaya Nabih (University of Sidi Mohamed Ben Abdellah of Fez, Morocco), Ismail Elhassnaoui (University Mohammed V, Morocco) and Abderrahim Lahrach (University of Sidi Mohammed Ben Abdellah of Fez, Morocco)
DOI: 10.4018/978-1-5225-9771-1.ch008

Abstract

The Innaoune Watershed represents an important hydric potential of the oriental part of Morocco. However, the basin exhibits a set of hydrologic drawbacks, such as floods, erosion, and pollution. This chapter is focused on flood forecast study. In order to help managers and decision makers to adopt the appropriate land management strategies for protecting the population from flood damages, the study of the hydrological behavior and quantification of water yield are paramount. According to this perspective, the main goal of this chapter is to test the ability of the SWAT model to simulate and reproduce the hydrological behavior of the upstream of Innaouene Watershed. The output of the model could be used to map, delineate, and forecast the floods expansion for a particular rainfall event. SWAT was performed on a daily time step from 2004 to 2012 for calibration and 2012 to 2014 for validation. The model accuracy was evaluated by measuring the Nash-Sutcliffe coefficient and R2.
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Introduction

Over the history of Earth development climate has known many changes, the end of the ice age 7000 years ago, marks the beginning of a new climate cycle (IPCC, 2007). Population growth and pollution combined withclimate change, are some of the main issues that decision makers face when managing the most important resource, which is water, especially in developing countries like Morocco, indeed the country has a complex climate variability characterized by a long period of drought, extreme evapotranspiration, and early or late rains (FalhiS.& al., 2016). The main sequels of these changes are; changes in precipitation patterns, excessive drought and heat waves, the hurricanes will become more devastating, and the sea level will rise 1-4 feet by 2100 (IPCC, 2013). Similar deviations will have a harmful impact on ecosystem balance generally, and human life specifically. According to the fifth report of the Intergovernmental Panel of Climate Changes (IPCC), a decrease of up to 20% in rainfall is predicted by the end of this century, and the increase in temperature is expected to reach 2.5 °C to 5.5 °C under the same scenarios (IPCC, 2015).

Not to mention the availability of water has decreased from 3500m3/person/the year 1960 to 1000m3/person/year in 2000, a drop of 420 m3/person/year in 2020 is predicted, and therefore the water demand will increase in the future (IPCC, 2014).

The three major sources of water pollution in Morocco are; municipal wastewater discharge, industrial effluents, and agricultural activities, urban area generate around 500 m3/year of wastewater, and it may reach 900 m3 in 2020. The high salinity and nitrate concentration affect the underground water, streams are generally contaminated by phosphorus, ammonia, organic matters, and high coliform counts. This polluted water is directly discharged to a natural water body, for example, Sebou watershed which constitutes 29% of Moroccan water resources is heavily polluted by nitrates, phosphorus and pesticide residues (EnnabliM. &al.,2017).

Even though Innaouene watershed presents an important hydric potential of the oriental part of Morocco, because of its geomorphological situation and its karstic reservoir, the basin faced a set of problems such as floods, drought and water quality.

In the last decay, a devastating flood caused important humans and materials damages, in 1973, a hydroelectric reservoir was built in order to manage water and mitigate the floods (OECD,2017). However, the area still suffers from several problems, which relay its socio-economic development.

In the other hand, Innaouene River’s tributariesareexposed to sewage and margins release. The sequels of such actions are not only limited in the river level, but they alsospread and may affect the groundwater, the reservoir (which is essentially used for irrigation), the neighboring area, and on sanitary and environmental field.

Moreover, the basin did not evade the impact of global climate change, this later present semi-arid climate that has two major phases; dry and humid, therefore, the hydrological cycle does not assure a complete water renewal since evaporation and evapotranspiration are limiting factors.

In order to help manager and decision makers to adopt the appropriate land management techniques, the study of the hydrological behavior and quantification of water resources is paramount. Hydrological models are important tools for managing and planning a sustainable use of water resource to meet various demands. According to this perspective, this chapter remains part of hydrologic simulation using the SWAT model, the study is axed as below;

Key Terms in this Chapter

Curve Number: A parameter that has a relation with land use and hydrologic soil properties of a watershed, and is used in the SCS method.

Available Water Capacity: Volume of water that can be held by the soil.

Hydrologic Cycle: A series of complex processes of water movement which is continuous, with its different states on the earth’s surface.

Hydrologic Response Unit: Unique combination between slope, land use and soil time which have the same hydrological behavior regarding water runoff.

Calibration: Estimation of non-measurable parameters on the field by decreasing the difference between the observed and simulated hydrograph using historical rainfall, flow, and current basin conditions.

Validation: Verification of model hydrograph using other time series while maintaining the same calibration parameters.

Hortonien Precipitation: The limiting curve when rainfall intensity surpasses the capacity of infiltration.

Interception: The portion of rainfall that gets trapped on the vegetation surfaces and return to the atmosphere usually through evaporation.

Hydraulic Conductivity: Indicates permeability of intercepted porous matter by the ratio of velocity to the hydraulic gradient in a given time.

ISRIC Database: International Soil Reference and Information Center is a dependent foundation formed by Dutch law in Wageningen University and research.

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