Watershed Management, A Tool for Sustainable Safe Reuse Practice, Case Study: El-Salam Canal

In Egypt, drainage and irrigation network receives a complex mixture of industrial and domestic effluent. Therefore, water quality was subjected to rapid deterioration over the past decades. A need for using marginal quality water in agriculture for new expansion projects is becoming a great necessity. Good quality water is no longer available for new irrigation projects. One strategy to increase available water resources is to reuse agriculture drainage water for irrigation. Surface water of low quality along with limitation of current water resources was found to be the largest current environmental threat to the drainage reuse practice in Egypt. The detrimental effects of drainage water reuse can be minimized by adopting appropriate pollution sources management. Although domestic diffuse sources represent very small portion of the total discharge in drains, they contribute to a high percentage of organic load to the water system. Lack of investment and time required to execute proper wastewater treatment plants (WWTPs), become a constrain impeding the improvement in surface water quality. The proper water quality management system along with good planning for constructing, upgrading and upscaling of WWTPs within a certain watershed can positively improve the water quality at the mixing point with fresh water for reuse. In this study, a practical management tool based on watershed as one of the primer water system unit has been introduced. The tool works under GIS environment to help water managers and planners concerned in irrigation system to incorporate the reuse of drainage water to set best prioritization scenario of WWTPs implementation, upgrading or upscaling within the sub-watershed of El-Serw and Bahr-Hadous drains that feed El-Salam canal. The study is based on analyzing the transport and decay of pollutants expressed as BOD load through network analysis of drains network within El-Salam canal watershed as a case study.


Introduction
Based on the measures towards water resources management, Egypt is facing serious challenges such as deterioration of water quality and the growing demand-supply gap (Mohamed 2013). In the 1980s, the reuse of agricultural drainage water became a policy in Egyptian water resources management practice (El Gammal et al. 2010). The amount of annually produced drainage water is 24.12 billion cubic meter (BCM/ year) extracted amount of 15 BCM/ year as surface water outflow (base year 2012) (MEWINA 2015). El-Salam canal is one of the most leading national water reuse projects in Egypt. The drainage water supplied to the project is essential for its sustainability. It is estimated to be 2 BCM/ year. This quantity is harvested from two main drains: El-Serw and Bahr-Hadous. This drainage water is mixed with another 2 BCM/year freshwater drawn from Damietta Branch, to produce a total discharge of 4 BCM/ year in order to supply enough water to irrigate 200,000 feddans in the western Suez canal region and 420,000 feddans in North Sinai.
Since the sub-watershed area of the two drains is located in a highly populated areas, the drainage system within the region is susceptible to pollution from legal and illegal dumping of domestic and industrial wastewater. Furthermore, the current proposed mixing ratio of 1:1 may be changed to a higher percentage of mixed drainage water, due to expected development in North Sinai and a limitation in fresh water. This might put more pressure on water managers and planners to go forward in improving the water quality of reused drainage water.
In 2005 a field study has done and was found that most of the water received by Bahr-Hadous drain (94.3%) is from agricultural diffuse sources. Although domestic diffuse sources contribute only 4% of the total discharge, this fraction contributes 94.7% of the organic load received by Bahr-Hadous, expressed as BOD load (EcoConServ 2005). This percentage of organic load resulting from domestic diffuse is almost the same for drains within El-Salam catchment area. Accordingly, the water quality of the canal has been negatively affected and the reuse plan of increasing the amount of mixing drainage water has been threatened. Therefore, and due to urgent need of irrigation water, important and immediate measures should be taken.
This study identifies watershed management as one of the premier water system unit for best water management. That occurring within the designated watershed rather than administration boundaries. The watershed of El-Salam canal can be classified into three main categories: 1-Fresh water source sub-watershed (Damietta Branch); 2-Mixing drainage water source sub-watershed (El-Serw & Bahr-Hadous drains) and finally 3-Irrigated sub-watershed of El-Salam canal (620,000 feddans). This study will focus on El-Serw and Bahr-Hadous sub-watershed which is located within five governorates (administration boundaries). The Watershed Approach is an ongoing cycle of tasks: setting standards for surface water quality; taking measurements of the conditions; assessing the data and identifying the impairments including establishing priorities; verifying the pollution sources and developing plans for restoring water quality and implementing pollution source controls (Texas Water 2018). Pollution source controls can be permits, rules, and source management practices. The plan should be set to better achievement of protecting watershed, which means clean water in the streams within watershed.
Watershed planning is a continuous process that requires: -Collect and analyze of water resources data to identify issues and problems; -Design a watershed plan on the basis of this data to protect and promote resource sustainability; -Implement the plan; -Monitor and evaluate the plan while continuously updating it to adapt to new information or technology; -Enforcement and compliance efforts.

Problem statement
Since the dawn of time, nature has known how to preserve the internal balance that contributes to a healthy and clean environment (ElKhazragy 2016). The continuous release of wastewater to the water network reaches the level that exceeded capabilities of a natural system to process the pollution resulting to a serious impact on the water quality, which affects the sustainability of reuse projects in Egypt. The low level of sanitation service especially in rural areas makes nearby streams (either canals or drains) the perfect places for inhabitants to dispose of their sewage (Shaban et al 2010). Most water policies adopted conventional strategies and continuing dumping in water streams without serious consideration to its environmental effects on downstream, and when considered, they were superficially touched within isolated administration boundaries and there is a lack of consistent analytical studies on the quantity of pollution load and the reduction target. This raises important questions: -Does water managers need to consider watershed, rather than isolated administrative boundaries in management and planning? -What water managers can achieve with limited funds in the near term to improve water quality of surface water? -What is the appropriate management approach for best implementation of WWTPs, taking into consideration the limited funds and fast impact to downstream water quality? -How much pollution load -expressed in BOD Total Maximum Daily Loads (BOD TMDLs) -is produced from mixing drains sub-watershed of El-Salam canal?

Research objectives
-The wide goal of this study is to contribute for solving the problem of water shortage in Egypt, by presenting the most proper management tool for better understanding the problem of pollution sources and plan for reducing pollution. -Production of environmentally safe drainage water suitable for disposal and/or reuse.
-Put best management tool for water quality management starting by considering point source of pollution (PSP) and ending up by considering all sources of pollutions including nonpoint source of Pollution (NPS).

Materials and Methods
The methodology is based on setting a practically distributed and physically based watershed-scale water quality model for estimating the movement of point sources BOD load through in surface water (case study: El-Serw and Bahr-Hadous drains sub-watershed). A pollution load assessment has been carried out by estimating BOD load at both source (upstream) and at mixing point (downstream) of the sub-watershed through the comparison analysis of transport and decay of pollutant (BOD Load) for best management within the study watershed in order to get safe water reuse practice (irrigation and fish farming). The study considers domestic diffuse sources (point source) as initial stage. The system has been designed under a Geographic Information System (GIS) environment, to support development of a comprehensive watershed simple model, for use as a tool for watershed planning, resource assessment and ultimately, water quality management purposes of El-Salam watershed (Appendix 1, shows a sample of the analysis result). The study considers only domestic sewage point  Vol.11, No.4, 2019 53 source within the study watershed by knowing how much pollution load is going to El-Salam canal, where it comes from, who is producing it, how it is being contaminated and where it is ends up.
Watershed are important because all point and non-point sources of pollution within the study area ultimately drain to other water bodies. It is essential to consider these downstream impacts when developing and implementing water quality protection and restoration actions. Whatever is dumped in upstream ends up downstream within the watershed. In this case, management and planning in a holistic approach (watershed approach) is much more effective rather than individual management within isolated administrative areas ( Figure  1).

Collecting data and building the network
The major steps in system application process consist of: 1. Collection and development of data; 2. Characterization and segmentation of watershed; and 3. Scenario analyses. The following detailed steps has been done: 1. A drains network of the study area has been built in a geographical database, as preparation to assist a network analyses based on watershed approach (Figure 2). 2. Digitizing of drains network within the watershed and specify the served area for each WWTP, population data, villages location and clusters planning; 3. The villages, WWTPs and area served by each treatment plant were located, a networking analysis was conducted as well as the determination of the flow of network paths. 4. Evaluate the efficiency of WWTPs within studied watershed: 67.5 % for El-Serw catchment, 68 % for Bahr-Hadous catchment area. Many of WWTPs in developing countries which were constructed outside of urban regions, have become surrounded by residential buildings. This has prevented the horizontal expansion of these WWTPs (Safwat 2018), accordingly, nearby unserved villages can be served by those WWTPs that have upscaling ability either horizontally or vertically within the same cluster according to land availability. The computational analysis of the network was made to calculate the decay rate of the organic load (BOD) for the distance from production at source to the mixing point with El-Salam Canal, considering villages and clusters as segment units using the decay equation: (1) Where BODo is the amount of the biochemical oxygen demand at x = 0; is the mean velocity in drains = 1 m/s, with a decay coefficient: k = 0.5, at average temperature=20 o C.

Urgent pollution treatment strategy:
This is can be achieved by two scenarios: 1-either by implementing new WWTPs within un-served areas; 2-Upscaling neighboring existing WWTPs to accommodate surrounding un-served areas; and/or; 3-upgrading unqualified existing WWTPs within served areas. The decision support system is designed to support analysis at a variety of scales using tools that range from simple to sophisticated. Figure 1: Two types of management divisions (administration and watershed boundaries) The methodology is based on pollution treatment strategy. Watershed management traditional approach typically involves many separate steps: collecting data, summarizing information, developing maps and tables, applying and interpreting models. The data can be classified into two categories: 1-Spatial wise data: geographic data; 2-Measurable wise: Quantity and quality data.
For initial quick decision, those interpretations do not require other information on hydrology, agriculture and land, which is not included in this study and can be considered in future studies.
The analysis conceived as a system for supporting the development of BOD Total Maximum Daily Loads (BOD TMDLs). Developing BOD TMDLs requires a watershed-based point source analysis for a point source of pollution. A geographic information system (GIS) provides the integrating framework for network analysis. GIS organizes spatial information so it can be displayed as maps, tables, or graphics. GIS provides techniques for analyzing compined information and displaying relationships.  55 -Capital cost for new WWTP less than 10,000 m 3 /day = 8000 LE/m 3 ; -Capital cost for new WWTP more than 10,000 m 3 /day = 10,000 LE/m 3 ; -Running cost for existing (treatment only) = 40~65 piasters/m 3 ; -Running cost (collection, pumping and treatment) = 1.5 LE/m 3 . The sub-watershed of the study area has been divided into villages and clusters ( Figure 3) and has been classified as:

Administration division (five governorates) Watershed division (two catchment)
-Served villages: those villages that have wastewater treatment facilities; -Un-served villages: those villages that have no wastewater treatment facilities; -Cluster: a geographical area that has more than one villages and can be served by one WWTPs; 3.1.1 Prioritization of building a new WWTPs within El-Salam watershed area Prioritization of the constructing new WWTPs has been identified within the sub-watershed of El-Serw and Bahr-Hadous drains. The analysis has been done through a GIS network to calculate the maximum organic load resulting from each village at the mixing point with El-Salam Canal (BOD Total maximum daily load). The GIS model has been built within the framework of the available information from Ministry of Housing, Utilities and Urban Development (MoHUUD) to determine the priorities from the perspective of water managers, where the geographic data of the villages, main and secondary drains of the study area has been adopted, along with the population data from the Holding Company for Water Supply and Sanitation (HCWSS 2016).This section aims to determine the priorities of the implementation of WWTPs in successive phases in order to reach the accepted quality of mixed drainage water on the El-Salam canal to the degree that commensurate with the importance of this project from both environmental and national prospective.  -1 st phase new WWTPs ( Figure 6) 10 plants; -Serving a population of 142,167capita; -With a capacity of 18,126 m 3 /day; -To remediate a total of BOD 7,677 kg/day; This end up to a reduction in the total BOD load of 7,677 kg/day at source and 6,597 kg/day at mixing point, by applying the treatment process for the 1 st 10 new WWTPs, the BOD will drop down from 11,078 to 3,401 kg/ day at source and from 9,952 kg/ day to 3,355 kg/ day of BOD at the mixing point.     Vol.11, No.4, 2019 Figure 9: Integrated framework for watershed management -The sum of treated sewage out of both scenarios= 394,892 m 3 /day representing 44.7 % of total production wastewater; -The reduction of the BOD load from 228,460 kg/ day to 63,333 kg/ day with a reduction percentage of 72.3 % at source; -Along with a reduction in BOD load from 174,860 kg/ day to 65,406 kg/day with a reduction of 62.6 % at mixing point with El-Salam canal. -Scenario 1: was to build 136 new WWTPs out of expected 454 WWTPs. -Scenario 2: was to upgrade 62 Existing WWTPs out of 83 WWTPs.

5-Conclusions
Using watershed management approach with a proper tool of analysis resulted in the best scenarios for mitigation of the problem of bad quality of mixing water within El-Salam watershed as follows: -Building of 30% of required new WWTPs along with upgrading 75% of existing WWTPs results in treating 44.7 % of total sewage water, 98 % of untreated sewage water, reducing BOD load with 72.3 % at source and 62.6 % at mixing point.