Quantitative Hyperspectral Analysis for Characterization of the Coastal Water from Damietta to Port Said, Egypt
Total Page:16
File Type:pdf, Size:1020Kb
ARTICLE IN PRESS The Egyptian Journal of Remote Sensing and Space Sciences (2014) xxx, xxx–xxx National Authority for Remote Sensing and Space Sciences The Egyptian Journal of Remote Sensing and Space Sciences www.elsevier.com/locate/ejrs www.sciencedirect.com RESEARCH PAPER Quantitative hyperspectral analysis for characterization of the coastal water from Damietta to Port Said, Egypt Islam Abou El-Magd, Ahmed El-Zeiny * National Authority for Remote Sensing and Space Sciences, Environment Department, 23 Josef Tito St., El-Nozaha El-Gedida, Cairo, Egypt Received 27 August 2013; revised 15 January 2014; accepted 16 February 2014 KEYWORDS Abstract The coastal zone of the Nile Delta is wealthy of natural resources that currently accom- Hyperspectral remote modate and support not less than one third of the population. However, it is still a promising area sensing; for energy resources and industrial activities that initiated the country to develop new action plans Coastal water quality; for industrial estates and services; it is under extreme environmental pressure. The newly developed Nile Delta; techniques of remote sensing offer effective tool to monitor such environment on a near-real time Egypt basis at minimum in situ sampling. Detection of water quality conditions and parameters is one of the major advantages of hyperspectral remote sensing technologies; which has been widely used to assess water quality conditions of many open water mass and aquatic ecosystems. This research looked at characterization of the water quality using the different functions of in situ measurements of hyperspectral sensors in conjunction with water quality multi-probe sensor. The spectral behav- iour of the water at the outlets is quite different from the other sampling sites of the coastal water. Turbidity was recorded at high level of 65 (NTU) and chlorophyll was up to 147 mg/l at the outlets, which were positively correlated with the hyperspectral curve of the spectroradiometer and Hype- rion data. The archived Hyperion data showed some similarities and differences with the in situ data that were mostly due to the timing differences between both datasets; it, however, enabled for understanding of the hyperspectral application in water quality. Ó 2014 Production and hosting by Elsevier B.V. on behalf of National Authority for Remote Sensing and Space Sciences. 1. Introduction The Nile Delta of Egypt represents about 2.3% of the Egyp- * Corresponding author. Tel.: +20 1007737052. tian territory; however, it supports 63% of the country’s agri- E-mail address: [email protected] (A. El-Zeiny). cultural land (Hereher, 2009) and accommodates about 45% Peer review under responsibility of National Authority for Remote of Egyptian population. Ecologically, it includes about 25% Sensing and Space Sciences. of the total Mediterranean wetlands (Sestini, 1992), which sup- ports the ecological balance and fishing production. The coast- al zone of the Nile Delta is wealthy of natural resources that Production and hosting by Elsevier currently accommodate and support not less than one third 1110-9823 Ó 2014 Production and hosting by Elsevier B.V. on behalf of National Authority for Remote Sensing and Space Sciences. http://dx.doi.org/10.1016/j.ejrs.2014.02.001 Please cite this article in press as: Abou El-Magd, I., El-Zeiny, A., , Quantitative hyperspectral analysis for characterization of the coastal water from Damietta to Port Said, Egypt, Egypt. J. Remote Sensing Space Sci. (2014), http://dx.doi.org/10.1016/j.ejrs.2014.02.001 ARTICLE IN PRESS 2 I. Abou El-Magd, A. El-Zeiny of the population (Abou El-Magd and Hermas, 2010). How- The content of chlorophyll-a is proportional to the amount ever, it is still a promising area for energy resources and indus- of biomass present in the body, while there is a relationship be- trial activities that initiated the country to develop new action tween reflectance and total suspended solids (Li et al., 2010; plans for industrial and services estates. Unfortunately, due to Moses et al., 2012). This includes classifying the trophic status the un-planned development activities the coastal zone and of lakes (Koponen et al., 2002; Thiemann and Kaufmann, coastal water resource are facing unprecedented pollution 2002) and estuaries (Froidefond et al., 2002) characterizing al- from human activities including agriculture discharge, indus- gal blooms and chlorophyll-a (Stumpf, 2001; Gitelson, 1992; trial discharge as well as sewage discharge. Simply, all kinds Polliainen et al., 2001; Gons et al., 2008) and assessment of of pollutants that are carried by rivers and drainage systems ammonia dynamics based on signatures of macrophytes (Tilley ultimately end up into these coastal water resources (El-Zeiny, et al., 2003). This would enable cumulatively to determine the 2010). total suspended matters (Hakvoort et al., 2002; Vos et al., To monitor the quality of such dynamic environment the 2003; Nechad et al., 2010) and total phosphorus (Koponen conventional methodologies are required to regularly obtain et al., 2002). water samples for laboratory analysis. However, these method- The main objective of this research paper is to characterize ologies are accurate and help in proposing mitigation and the water quality of a portion of the coastal zone of the Nile rehabilitation mechanisms, they have some shortcomings. Delta using the different functions of in situ measurements of These include the localized sampling location that could not hyperspectral sensors in conjunction with water quality mul- be generalized, does not consider the other surrounding envi- ti-probe sensor and remotely sensed data. ronment that influences the water quality as well as time con- suming and very costly. Therefore, new techniques of earth 2. Materials and methods observations including the availability of repetitive, synoptic and multi-spectral data from various satellite sensors are pow- 2.1. Area of study erful in monitoring the coastal and marine environment (Nayak, 2002). Such remote sensing tools provide near-real The chosen area of study is an elongated coastal zone area that time monitoring of such dynamic environment. extends from Damietta to Port Said. It represents a vital part Hyperspectral remote and proximal sensing is currently of the Nile Delta region as a resource for fish production, en- extensively and successfully used to study the state of the envi- ergy and some of the industrial activities. It witnessed lots of ronment and to track changes that occur over time. It acquires changes during the last few decades and greatly affected by dif- intensive, very narrow and contiguous spectral bands through- ferent types of man-made activities and changing of the land out the visible, near-infrared and mid-infrared portions of the use and land cover of the surrounding area. This boosts the electromagnetic spectrum (Song et al., 2012). Hyperspectral discharge of pollutants from various types and sources of sensors typically collect 200 or more bands enabling the con- wastes, which negatively affect the region (Fig. 1). struction of an almost continuous reflectance spectrum for The climatic condition of the area is typical Mediterranean every pixel in the scene. Contiguous, narrow bandwidths char- environment with moderate temperature most of the year. The acteristic of hyperspectral data allow for in-depth examination obtained meteorological data are from the nearest climatic sta- of earth surface features which would otherwise be ‘lost’ within tion at El Gamil station in 2011 (Table 1). The predominant the relatively coarse bandwidths acquired with multispectral wind direction in the area of study is almost northwest direc- scanners (Smith, 2001b). tion most of the year, which creates a general eastward-flowing Hyperspectral remote sensing has shown high potential in long shore current (El-Asmar and Hereher, 2010). Statistically, detecting the conditions of the water quality and its parame- it was found that 81% of these waves originate from the north- ters. This is actually based on the interaction between the elec- west direction, 14% from the northeast and just 5% from tromagnetic radiation and the water contents. The shorter the southwest (Frihy et al., 2003). Winter season almost records wavelength the higher is the penetration of the water content, the maximum wave height of 4.2 m which is predominantly which reflects the water column, therefore both wavelength from the west-north-west wave direction; whereas spring sea- and water characteristics are key in this process. In fact, the son records the minimum wave height of 1.16 m which origi- reflectance of the water surface is the result of complex pro- nates from the northwest direction (El-Banna 2007). A tidal cesses of absorption and reflection of sunlight by phytoplank- difference is semi-diurnal and ranges between 25 and 30 cm ton, inorganic particles in suspension, dissolved humus, water along the delta coast. plants and water (Malthus and Dekker, 1994). In this context, the narrow intervals of hyperspectral channels enable a wide 2.2. In situ measurements range of reflectance that is useful in assessing water quality conditions of many open water aquatic ecosystems like our area of study. Unfortunately, this might not be the case in Two systems of in situ measurements were carried out, which all environments where there are surrounding land use and include measuring the physico-chemical parameters of coastal land cover that influence the water characteristics and thereaf- water using