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Geo-hydrological Study of Groundwater
Artificial Recharge in Madoneh Area [/center]
Introduction
The need for artificial recharge is to store surplus surface water underground that is expected to increase as growing populations demand more water. A worrying aspect is that the number of sites with sufficient infiltration capacity becomes fewer every time a Retention Dam is being constructed.
Actually, artificial recharge may be used to store treated sewage effluent and excess storm water runoff for later use. Groundwater recharge may also be used to restore groundwater levels in over-exploited aquifers and mitigate or control saltwater intrusion into coastal aquifers.
However, in order to accomplish the use of artificial recharge without deleterious environmental consequences, the optimum combination of treatment methodologies before recharge and after recovery from the aquifer must be identified.
It will also be necessary to consider the sustainability of soil-aquifer treatment and health effects of water reuse when using treated wastewater as the recharge medium.
1- 1 Artificial recharge in Jordan
The main purpose of the application of artificial aquifer recharge technology is to store excess water for later use, while improving water quality (decreasing the salinity level) by recharging aquifers with water of better quality. There are several artificial recharge techniques in use including infiltration basins and canals, water traps, cutwaters, surface runoff drainage wells, septic-tank-effluent disposal wells, and the diversion of excess flows from irrigation canals into sinkholes(USAID,FS/AR,1997).
Scarcity of water resources in Jordan is the major inducement for seeking new techniques to diminish declines in the groundwater level and deterioration of water quality. Artificial recharge is one of the important methods to solve water shortages in Jordan and methods as described above appear to be suitable for local circumstances and capabilities.
The introduction of artificial recharge in Jordan is only of a very recent nature. Feasibility studies have been carried out around the year 2000 to find out whether conditions in Jordan are suitable to introduce artificial recharge schemes using surface runoff (rain) water. One of those studies was carried out by the Ministry of Water and Irrigation in cooperation with USAID (Chehata,1997). The study focused on the Wadi Madoneh and the Wadi Butum areas, located northeast of Amman. Upon completion of the study, the conclusion drawn was that Wadi Madoneh offered the best scopeforthe implementation of artificial recharge. .
Figure 1.1
View on Wadi Madoneh hydrological monitoring station in the middle
1 – 2 General Background
The Ministry of Water and Irrigation (MWI) of Jordan and UNESCO-IHE, Delft did subsequently agree to carry out a pilot study on artificial recharge with surface water in the Wadi Madoneh area.
The project is funded by the Ministry of Foreign Affairs of The Netherlands and is undertaken in the frame of the EXACT project[1]. The duration of the pilot study is five years, starting on the first April 2002. However, the project has been extended in 2006 and now runs up to April 2010.
The original project document has distinguished three phases. A first phase of two years for measuring parameters, a second phase of one year for the construction of the infiltration works and finally a third phase of two years for monitoring the performance of the infiltration works.
Connected to the first phase of the project is an MSc study that will use the collected data for Wadi Madoneh. Up to now, more than 3 years of data is available. The joint supervision of the study was carried out by Mu’tah University, Ministry of Water and Irrigation in Jordan, and UNESCO -IHE in The Netherlands.
Data collection has been as follows. In the autumn of 2003 two automatic rain gauges were installed in the basin, and two groundwater observation wells were equipped with data loggers for groundwater level measurements. At the outlet of the upper Wadi Madoneh catchment, a hydrological station was constructed whereby two stilling wells were built to measure water depths in the wadi (see figure 1.1). In the spring of 2004 the observations of these instruments for the first wet season have been collected. This is one year later than anticipated due to unforeseen problems with the purchase and installation of the equipment.
1 – 3 Problem description
Wadi Madodeh is located within the desert agro-climate zone where precipitation rates are being in the order of 150 mm/year. The majority of the rain comes in the form of outbreaks of thunder rainfall. The surface runoff is characterized by flash floods generated by the rainfall mode and the topography in the area. The potential evaporation far exceeds the rainfall in this semi-arid area.
The main aquifers for groundwater supply for Amman city are the Wadi As-Sir limestone and the Amman Silicified limestone. These limestones are also present in the upper Wadi Madoneh area where they outcrop in the north and are covered by younger geological formations in the south. The rather unfair and uncontrolled abstraction of water from numerous wells in the area in addition to the scarce precipitation has caused that groundwater depletion and water quality deterioration to occur.
As mentioned previously the main underlying problem for the Wadi Madoneh area and the aquifers are the increasing demands on groundwater for agricultural, industrial and domestic purposes, while the scarcity of groundwater is a Pressing fact for the region.
1 – 4 Objectives of the Study
The following objectives have been defined for the present study :
1. Evaluate the potential for artificial recharge considering the general hydro-geology and the scope for infiltration in the area. The recharge will be based on the use of excess surface water to augment and improve groundwater resources and thereby reduce the rate of depletion of the underground water resources;
2. Develop ideas on the artificial aquifer recharge technology to be used and select recharge locations. This all to store excess water for later use, while improving water quality (decreasing the salinity level) by recharging the aquifer with better water;
3. Assist in the establishment of the effect of recharge by flood water on the groundwater system presumably made up of fractured and karstic limestone in the Madoneh area;
4. The effect will primarily be considered in terms of the quantitative impact exerted on the geo-hydrology of the system, but qualitative (water quality) aspects may also be considered. The system is reported to be over exploited; at least in the wider Amman area.
1 – 5 Methodology
Carefully selected methods have been followed to assess the hydrogeology for the area and infiltration capacities. The suitability of the locations selected for artificial recharge, and the optimum artificial recharge method have been verified. There are several artificial recharge techniques in use, including infiltration basins and canals, dams, water traps, cutwaters, surface runoff drainage wells, septic-tank-effluent disposal wells, and diversion of excess flows from irrigation canals into sinkholes.
A further approach was to study the area without and with the implementation of the proposed infrastructure for the infiltration of the flood water. Important elements here are the assessment of the hydro-geology and geo-hydrology of the area, the analyses of time series, the classification of the groundwater quality, the development of water balances, and possibly the execution of groundwater modelling to assess the impacts. The detailed elements of the methodology are:
1-5-1 Without artificial recharge techniques
1. Study preparation and field work
Familiarization with existing reports and data was the first step in the present work. Further geological reconnaissance, a well inventory including water sample collection in the field has been carried out.
2. Hydro-geological assessment of the study area
Based on an existing geological map, field notes, additional structural information, and geological sections a hydro-geological map and hydro-geological sections were prepared. The first step was upgrading of the geological map. Then the transformation into a hydro-geological map and sections have been done. Permeability assessments have been added to the hydro-geological map and sections.
3. Analyses of the geo-hydrology of the groundwater system
Available for the analyses are: spreadsheets with time series of Madoneh groundwater level data and the field-collected regional groundwater level data. An analysis of the interaction between rainfall, floods and groundwater level behavior (and pumping at the chicken farm) was carried out. Regional groundwater level contour maps and an analysis flow directions have been prepared and including an assessment of the correctness of the elevations of the boreholes.
4. Evaluation of groundwater quality
Analyses of water samples of water pumped within the Madoneh area to evaluate the groundwater types in the study area, and evaluate the water quality against standards, along with evaluation of the surface water quality (floods).
5. Establishment of ground water balance components for the area
Available for the establishments are: set-up for the water balance. The main task is to complete the water balance analyses and to find out the quantities of water involved. Groundwater and surface water quantities for the water balance components may be estimated.
1 -5 -2 With artificial recharge techniques
1. Verification of sites for artificial recharge works
A second hydro-geological map was produced showing the infiltration capacities (qualitative), mainly along the wadi courses. Based on the results of the infiltration capacity mapping, the locations of sites for artificial recharge were determined (Retention Dams). The correctness of the locations of the selected sites has been verified. Based on a literature study concerning artificial recharge methods, the most suitable method for the Wadi Madoneh area was selected
2. Identification of changes on the geo-hydrology
According to artificial recharge techniques, any changes in groundwater levels will be predicted considering the regional geo-hydrological map and the groundwater level time series in relation to floods and rainfall.
3. Establishment of changes in the ground water balance components;
The water balance analyses have been completed to identify quantities of water available to recharge the aquifer within the study area as well as predict water balance for the long term.
4. Recharge effects based on groundwater quality:
Effects on groundwater quality have been forecasted. The methodology here consisted of a study comparing the existing groundwater quality with the water quality of the storm water.
1 -6 Available data
A wide range of data is available including geological maps and photos, geophysical surveying and well logging data and borehole lithological data, groundwater level measurements, infiltration data, abstraction data, designs, pumping test analysis, groundwater samples for water quality analysis, rainfall and runoff data, and climate data including potential evaporation data.
1 – 7 Fieldwork
The MSc fieldwork within the study area included visits to the regional wells in the area including those in Wadi Ishsha, the Tamween area, the phosphate mining area and the industrial area in Zerqa. Visits were also done to the groundwater level monitoring and surface water stilling wells equipped under the EXACT project. Well visits included the checking of water levels, taking the water quality (EC measurement), and assessing the production of the wells that are pumping.
[CENTER]Figure 1.2
Wadi Madoneh with flood water
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Further activities included the classification of the soils for infiltration assessment, inspection of the geology and tectonics to complete the geological and structural map. On one occasion the area was visited during the occurrence of a flash flood and photos were taken to preserve this event (figure 1.2).