**1. Introduction**

Irrigated agriculture is important to the national economy of a country as it contributes significantly to the production of food. The main objective of irrigated agriculture is to enhance crop production for food sufficiency, particularly in semi-arid and arid zones [1]. It has contributed positively to food security, poverty alleviation, and rural development. In addition, it protects plant against frost, suppresses growing of weeds in grain fields, and prevents soil consolidation. Most irrigation schemes are faced with problem of soil deterioration resulting

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

from increased level of soil salinity and rise in water table. Soil salinity affects soil chemical, physical, and biological characteristics of the soil, fertility, and sustainable productivity unless it is properly monitored. Geo-informatics involves a combination of special techniques, technologies and tools for the acquisition, processing, management, analysis, and presentation of geospatial data [2]. It is a combined method to GIS and remote sensing. Remote sensing and GIS are well established information tools, since they give reasonable pictures of the entire process in spatial and temporal terms. They both provide a cost effective and adequate understanding of landscape dynamics, detect, identify, map, and monitor differences in land use and land cover pattern over long period of time [3]. The application of Satellite Remote Sensing (SRS) and GIS has been proved useful and successful in many fields such as natural resources management, agriculture, and environmental issues and water resources. Remote sensing approaches are very effective for detecting, monitoring and control of soil salinity. Remotely sensed data are used to assess soil salinity either on bare soils with salt crust or through biophysical properties of vegetation as these are affected by salinity [4].

**1.3. Impact of irrigation on vegetation and soil**

as marginal are now being cultivated [11].

**2. Characterization of soil salinity**

The practice of irrigation sometimes has an adverse effect on environmental condition otherwise properly monitored, planned and managed. Past record claims that human activities have a strong effect on the natural environment and becoming the main cause of environmental degradation [9]. The expansion of irrigation project has many advantages. However, largescale irrigation projects changes natural ecosystem. To undertake large irrigation projects, vegetation cover needs to be cleared and different construction activities needs to be done. Natural vegetation is an eminent parts of the ecosystem negatively affected with large-scale irrigation projects [10]. Soil being a vital natural resources, it has been assisting the increasing number of life on earth. As regards to increase in population, food demand also increased. This in turn put-size pressure on land/soil resource, areas of land that are formerly considered

Geospatial Analysis for Irrigated Land Assessment, Modeling and Mapping

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Mougenot et al. [12] argues that visible reflectance of leaves from plants growing on nonsalt affected leaves before plant maturation is higher than after maturity. In addition, visible reflectance of leaves from plants growing on salt affected soil is lower than the visible reflectance of plants growing on non-salt affected soils. Near-infrared reflectance increases without water stress due to a succulent (cell thickening) effect and increases in other cases. Spatial information on soil moisture can be accessed through bands in the near- and middle-infrared spectral bands; this is confirmed by [13]. The study showed that near- to middle-infrared indices are indicators for chlorosis in stressed crops normalized difference for TM bands 4 and 5. This new ratio is however dull to color variations and provides an indication of leaf water potential. In addition [14] showed that chlorotic canopies could be distinguished from healthy canopies, as biophysical response to a salinity can be seen in low fractional vegetation cover, low leaf-area index (LAI), high albedo, low surface roughness and high surface resistance compared with healthy crops. This is because healthy vegetation absorbs most of the visible light hitting it and reflects a large portion of the near infrared light. However, sparse vegetation (right) reflects more visible light and less near infrared light [15]. Traditionally, electrical conductivity (EC) measured in dS/m is used to determine the soil salinity on a small field with the aid of hand-held conductivity meter, while on a large scale it is measured and mapped using electromagnetic (EM) conductivity meter [15]. These approaches (traditional and geospatial) are used to quantify the density of plant growth on the earth visible radiation minus near-infrared radiation divided by near-infrared radiation plus visible radiation result-

ing into vegetation indices [16]. **Table 1** gave the criteria for classifying soil salinity.

During the last decade, there has been a proliferation of geospatial data in natural resource management including in the disciplines of forestry, fishery management, geology, geomorphology,

**2.1. Geographical information system in soil salinity modeling**
