Evaluation of Groundwater Part B. Water Quality in the Gaza Strip Municipal Wells. Water Resources Directorate

Transcription

1 State of Palestine دولة فلسطين سلطة المياه الفلسطينية Evaluation of Groundwater Part B Water Quality in the Gaza Strip Municipal Wells Water Resources Directorate Sept, 2013 i

2 Table of Content List of Figures ii Preface iii 1. Introduction Objective Background Groundwater Quality Records Assessment Chloride Concentration Records Assessment Sea Water Intrusion Trends Continuous Increasing Trends Steady with Low Salinity Trends Steady with High Salinity Trends Fluctuating Trends... Error! Bookmark not defined. 5. Nitrate Concentration Records Assessment Chloride Concentration Prediction with Time for Year 2017 and Conclusion and Recommendations i

3 List of Figure Fig. 1: Location map for Gaza Strip with municipal wells... 1 Fig. 2: Chloride concentration maps for year 2008, 2010, and Fig. 3: Location of municipal wells that affected by seawater intrusion Error! Bookmark not defined. Fig. 4: Seawater intrusion attitude... 4 Fig. 5: Location of municipal wells that affected by continuous increasing... 5 Fig 6: Continuous increasing attitude... 6 Fig. 7: Location of municipal wells representing the steady with low salinity attitude... 6 Fig 8: Steady trend with low salinity attitude... 7 Fig 9: Location of municipal wells representing the steady with high salinity attitude... 7 Fig. 10: Steady with high salinity attitude... 8 Fig. 11: Location of municipal wells representing the fluctuating attitude... 8 Fig. 12: Fluctuating attitude... 9 Fig. 13: Chloride values for Gaza Strip wells in Fig. 14: Nitrate concentration maps for year Fig. 15: Nitrate values for Gaza Strip wells in Fig 16: CL and No 3 combined concentration values for Gaza Strip wells in Fig 17: Prediction of Chloride Concentration for the Years 2017 and 2022 in Gaza Strip 12 ii

4 Preface The water quantity available to the population in Gaza is inadequate; and the water quality falls well short of accepted international guidelines for potable. The UN report "Gaza in 2020, a liveable place?"; issued August, 2012 has highlighted that Gaza aquifer will not be usable by 2016 and will be irreversibly damaged by This aquifer failure has been characterised by many commentators as a humanitarian crisis and accordingly the continuation of the status quo is rejected to be an acceptable option. The (PWA) calls for the support to translate International Commitments, represented by the UN relevant resolutions on water as human rights into enforceable National Mechanisms, otherwise; International humanitarian responsibilities towards Palestinians in Gaza will be faced by insolvable challenges soon. PWA has been trying; in spite of the extraordinary challenges; to manage the scarce water resource through a continuous process of monitoring and evaluation of the Coastal Aquifer degradation in terms of Quality and Quantity as reflected in this document which is composed of two parts: Part A: Water Level Assessment, and Part B: Water Quality Assessment. PWA deeply appreciates the effort exerted by its Water Resources Department team, who have been trying to clearly identify the aquifer's behavior; with special dedications to Mr. Hazem Zaqout and Mr. Jehad Desht and Mr. Ahmad Yaqubi for his support to the team. Rebhy El Sheikh Deputy Head, September, 2013 iii

5 1. Introduction: The Gaza Strip is located on the south eastern corner of the Mediterranean Sea, the width ranging of between 5Km in the middle to 8Km in the north and 12Km in the south. Its length is approximately 40km along the coastline and its area is about 378km 2, and is divided into five governorates, the North, Gaza, middle, KhanYounis and Rafah. These governorates contain 25 municipalities that provide the population of the water services, for total population of about 1.64 million inhabitants. Groundwater is the main source of water in Gaza strip (fig.1), and the Gaza people depend on groundwater as the only source to provide them with water used for drinking, agriculture, and industry. The Gaza Strip is supplied with water for domestic uses through 213 groundwater municipal wells, the operation of these wells are under the responsibility of the Coastal Municipalities Water Utility (CMWU), as well as the 25 municipalities which serve the population by pumping the water from these wells through the water networks for each municipality. Since Palestinian Water Authority (PWA) is the regulatory body for water sector in terms of environment quality and economic, therefore PWA is evaluating and assessing regularly the quality of the groundwater supplied as a matter of health protection as well as water management and planning. 2. Objective: This report will throw lights on the groundwater quality in terms of the concentration trends of chloride and nitrate for all municipal water wells in Gaza Strip. And focusing on the suitability of that supplied groundwater for drinking purposes is Gaza Strip taking in consideration the World Health Organization (WHO) standards and PWA standards as a reference. Fig.1. Location map for Gaza Strip with municipal wells 1

6 3. Background: The monitoring of groundwater quality in the Gaza Strip conducted twice per year (two cycles), the first cycle starts at the beginning of April (spring cycle), and the second cycle starts at the beginning of October (autumn cycle). Laboratory of Ministry of Health (MOH) is responsible for the collection and analysis of the water samples from the municipal wells in coordination with the municipalities. MOH analyzes groundwater samples for full chemical parameters including chloride and nitrate (CL, NO 3, EC, TDS, NH4, SO 4, Ca, Mg, Na, K, F, Alkalinity and hardness). After that, the results submitting to the Palestinian water authority (PWA) for the purpose of assessment and evaluation. As a result the water quality in terms of chloride and nitrate concentrated has been presented in graphs and maps. Chloride map is an indication of the salinity changes due to either up-coning or seawater intrusion, while the nitrate map as an indication for both agricultural activities and waste water percolation to the underneath aquifer through the unsaturated zone. 4. Groundwater Quality Records Assessment: More water was pumped from the aquifer than was recovered. This over extraction from the aquifer has resulted in drawdown of the groundwater with resulting intrusion of seawater and up-coning the underlying saline water. The major water quality problems are high salinity and high nitrate concentrations. In general, the groundwater salinity in terms of Chloride (Cl) changes from area to another, based on the hydrogeological condition of the water yielding zone, abstraction pattern in terms of quantity and duration as well as the total penetrated depth Chloride Concentration Records Assessment: Based on the result analyses of chloride concentration of the different wells in Gaza Strip a three chloride contour maps have been prepared showing the change of the chloride concentration for three years intervals (2008, 2010and 2012) for the purpose of showing the degradation trend (fig.2.). It is clear that area of fresh water is demolished and /or reduced significantly with time as a result of intensive pumping as well as the deficit in the water balance. Where, the magnitude of fresh groundwater body decreased in the North and southern parts of Gaza Strip which is originally characterized by fresh groundwater (CL < 250 mg/l). The effect of sea water intrusion has clear influence in the Western part of the Gaza Strip along the shore line especially in both the Western Gaza and Khan Younis governorates. Where, the Chloride concentration is in the range of more than 2000mg/l and to about 8000mg/l in some wells. In 2012, seawater intrusion phenomenon has reached to more than 2 km in land of Gaza City aquifer. 2

7 Fig.2. Chloride concentration maps for year 2008, 2010, and 2012 The chloride concentration map for year 2012 illustrate the majority of Cl concentration in the Gaza coastal aquifer ranges became between 600 mg/l to more than 1000 mg/l, This is due to the over pumping from the wells, Scarcity of rain, drilling municipal wells in a random manner and not distributed in an orderly manner resulting to sea water intrusion, lateral flow of brackish water from east in the middle and southern area and up-coning of the brine water from the base of the aquifer. Seawater intrusion and uplift the deep brine water are the direct consequences of over pumping, and represent the greatest threats to municipal and agricultural water supplies in the Gaza Strip. Based on the historical water quality of the different wells, it can be concluded that the magnitude and attitude of that change is controlled by many factors such as; well location, total depth penetrate, pumping rate and the hydrogeological nature of the underneath water bearing formation. Where the wells that are located in the eastern part of Gaza strip are characterized naturally by relatively high chloride content and its concentration is more or less constant with time or of slight increase. The coastal aquifer in that area is characterized by high chloride content which is originated as a result the lateral western flow direction. The Cl concentration of such wells is relatively high ( mg/l) as shown in fig.2 On the other hand, the trends of the historical Chloride concentration of the different municipal wells in Gaza Strip can be classified into five categories such as: Sea water intrusion trends. Continuous increasing trends. Steady with low salinity trends. Steady with high salinity trends. Fluctuating trends. 3

8 4.1.1 Sea Water Intrusion Trends: This trend occurs mainly in the wells that are located in Western and Northwestern part of the Gaza Strip and varies in magnitude and attitude from one well to another, based on the well location, the total depth penetrated and the pumping in term of rate and duration. More groundwater was pumped from the aquifer than was recovered. This over extraction from the aquifer has resulted in drawdown of the groundwater with resulting intrusion of seawater and up coning the under lying saline water. In year 2012 the intrusion of saline water into the Gaza costal aquifer is occurring at many locations along Gaza coast as shown in fig.3. On the other hand, the same situation occurs in the Khan Younis governorate in particular at El Mawasi where, the removal of sand dunes and drilling several wells for agriculture add additional pressure on the aquifer accelerating the seawater intrusion. The sea water intrusion phenomena occupied nearly about 15 % of the total wells (31 wells). Fig.4illustrates the trends of some selected wells representing the seawater intrusion attitude for different locations in Gaza Strip. Fig.3. Location of municipal wells that affected by seawater intrusion Fig.4. Seawater intrusion attitude 4

9 4.1.2 Continuous Increasing Trends: This trend occurs mainly in the wells that have historically low chloride content and which generally penetrate the upper part of the fresh aquifers that are located either in the northern or in the southeastern part of the Gaza Strip. This trend results from the up-coning of the highly saline water from the underlying aquifer caused by the intensive pumping and lowering of the groundwater level which, in turn, permits the upward leakage of the saline groundwater.fig.5 illustrate the location of these wells, where the locations either at the East and center of Gaza strip which affected by two factors, the upcoming of the underneath saline groundwater and the saline water coming from the East by lateral flow. Where, the original chloride content of the groundwater in these wells was relatively low (250mg/l) and increased gradually with time and with pumping. The salinity of the pumped water will continue increase with the same magnitude and trend. While in the wells that are located to the West are affected either by the saline water originated from the transitional zone or Fig.5: Location of municipal wells that affected by continuous increasing from the uplift of the deeper brine water, where the original chloride content of the groundwater was fresh and increased gradually with time and with pumping. The salinity of the pumped water will not continue increase with the same magnitude and trend as well as the wells affected by the seawater phenomena mentioned before. This phenomenon covers nearly about 30 % of the total wells (64 wells). Fig.6illustrates the trends of some selected wells representing the continuous increasing attitude for different locations in Gaza Strip. 5

10 Fig.6. Continuous increasing attitude Steady with Low Salinity Trends: This trend occurs where the water salinity is more or less constant with time and occurs mainly in the wells that are located in the Northern area of Gaza Strip, which is characterized by relatively high aquifer thickness that has high storage capacity of fresh water, in addition to the high transmissivity of the saturated layers, as well as its high productivity, in addition to the high permeability of the upper unsaturated layers which increases the infiltration capacity through This phenomena is occurred sand dune area. in the Southern area where the salinity is relatively high compared to Northern area, where the southern area is characterized by thin aquifer, low storage Fig.7. Location of municipal wells capacity of fresh water, less saturated zone, high representing the steady with low salinity attitude thickness of clay layer that minimizes the infiltration capacity and low rainfall (Fig.7).This phenomena occupied nearly about 26 % of the total wells (56 wells), and representative wells of this phenomena is shown in fig.8. 6

11 Fig. 8. Steady trend attitude with low salinity Steady with High Salinity Trends: This trend occurs where the water salinity is high constant with time and occurs mainly in the wells that located either in the along eastern area of Gaza Strip, or in the along center of Gaza strip fig 9. The coastal aquifer in the eastern areas is characterized by high chloride content which is originated as a result the lateral inflow of brackish water. While the wells which are located along the center of Gaza strip penetrating the highly saline water bearing horizon. This phenomena occupied nearly about 19 % of the total wells (40 wells), fig.10 illustrate the trends of some selected wells representing the steady with high salinity attitude for different locations in Gaza Strip. Fig. 9. Location of municipal wells representing the steady with highsalinity attitude 7

12 Fig.10: Steady attitude with high salinity Fluctuating Trends: This trend occurs where the groundwater salinity is originally high and in constant with time and occurs mainly in the wells that located either in the Eastern area of Gaza Strip close to the Eastern borders, or in the southern area of Gaza strip close to the southern borders,(fig.11). The wells in those areas are affected by the following factors; depth of these wells which are penetrated the water bearing horizon of high salinity, the lateral groundwater flow from the Eastern side and the pumping rate from these wells as well as from the Surrounding wells. This phenomenon covers about 3 % of the total wells (6 wells). Fig.12, illustrate the trends of some selected wells representing the fluctuating attitude for different locations in Gaza Strip. Fig.11. Location of municipal wells, representing the fluctuating attitude 8

13 Fig.12. Fluctuating attitude Based on this study, the increase in chloride levels in the municipal wells is considered a clear signal of the occurrence of seawater intrusion in Gaza strip accordingly chloride variable is taken as an essential indicator and reference point reflecting seawater intrusion phenomena. One results of the study reported that the intrusion of saline water into the Gaza costal aquifer is presently occurring at many locations along Gaza coast. The problem has become increasingly serious in recent years as demands for water from coastal aquifer have expanded. It was also observed that the Chloride concentration in the municipal wells ranges from 250 to more than 5000 mg/l. 25% of them had chloride concentration less than 250 (WHO allowable limit) while the remaining (75%) exceeds the WHO chloride level (fig.13). Fig.13. Chloride values for Gaza Strip wells in Nitrate Concentration Records Assessment: Nitrate levels in the Gaza Strip have continued to rise and currently present a health risk throughout the territory. High quantities of nitrates in drinking water can have significant health repercussions, particularly for infants. Application of fertilizers and pesticides in agricultural areas is the main reason of increasing nitrate level in groundwater. In addition to agricultural activities, nitrogen released from wastewater discharge plays a big role in aquifer pollution. Different factors affect the amount of nitrate pollution in groundwater resulted to 9

14 nitrogen load at the land surface. Such factors could be fertilizers and manure application rate, thickness of unsaturated zone, crop management, and form of applied nitrogen. The historical records of the nitrate concentration in the municipal wells refer to unclear attitudes for all wells, where the presence of the nitrate in the groundwater depends on spot sources of pollution in the area surrounding the wells, and thus the increasing of the sources of pollution cause the increasing of nitrate concentration levels in the wells respectively. On the other hand, the sampling way from the wells as well as the analyses methods play additional role in determining the unclear trends for the wells, where the duration of pumping before collecting the sample is affecting the final results, Therefore prefers to pump an appropriate amount of water for sufficient of time from the well before collecting the samples, to get actual nitrate concentrations in the aquifer. Based on the latest result of chemical analyses and the nitrate concentration map for the year 2012 (fig.14), the following points can be concluded: Fig.14. Nitrate concentration maps for year 2012 There are four zones have the nitrate concentration less than 50 mg/l (WHO allowable limit), these zones are located in the center of north governorate, Al Zahra and Al Moghraqa areas, east of middle governorate and the southeast of southern governorate, where these areas characterized by limited agricultural activities as well as the sewerage system. The urban centers such as Gaza city, refugee Camps in the middle governorate, KhanYounis and Rafah have Nitrate concentrations more than 200 mg/l, the reasons of that are, the leakage from sewerage network as well as the leached wastewater from cesspits in these areas particularly KhanYounis and Rafah. Generally the Fig.15. Nitrate values for Gaza Strip wells Nitrate concentration in the municipal in

15 wells ranges from 50 to more than 300 mg/l % of them had Nitrate concentration less than 50 mg/l (WHO allowable limit) while the remaining (73.5%) exceeds the WHO nitrate level as shown in fig.15. Taking in consideration the combined concentrations of both chloride and nitrate, it's clear that 6.5% of the domestic water is only matching with WHO drinking limit, while the remaining 93.5% is out of limit (fig.16). Fig. 16. CL and No 3 combined concentration in Chloride Concentration Prediction with Time for Year 2017 and 2022 Based on the water quality graphs magnitude as well as the attitude, taking in consideration the current abstraction status, the abstracted groundwater quality has been predicted for the years of 2017 and 2022 (Fig.17). It is obvious that the groundwater salinity will increase dramatically with time and with continuous pumping the salinity of the groundwater will increase and by that water quality of all the wells will be out of the international drinking limit, the reasons behind groundwater quality degradation as well as depletion that there is no balance between the renewable aquifer water amount and the total abstraction which is three time of the renewable and that deficit will increase with time. With the absence of alternative water resources in the short-term, there will be a real catastrophic water situation in the Gaza Strip 11

16 Fig. 17. Prediction Chloride Concentration (2017 and 2022) 7. Conclusion and Recommendations Only 6.5% (14 wells) of the groundwater pumped from the domestic wells in Gaza Governorates are matching with the WHO standard for drinking use. Seawater intrusion has becomes a fact, and it was observed in many locations along Gaza coastal line as a result of the over pumping as well as the un-equilibrium of the hydraulic system. Most of the coastal area and with a distance of about 2-3 km in land is affected by the sea water intrusion phenomena with different degree. The main factors controlling the sea water intrusion magnitude and attitude is controlled by the wells location, total penetrated depth and the pumping capacity. With the continuation of the over pumping, the sea water intrusion influence will expand in land with time to cover more area and wells. Wells, which are located in seawater intrusion zones, must stop pumping to reduce the deterioration in these zones and prevent the expansion of the phenomenon of seawater intrusion. Wells, which are located in the continues increasing trend zones, should reduce production of them to minimize the increase of chloride concentration in order to prevent the expansion seawater intrusion influence, specifically of the wells close to the coast. 12

17 The pumping rate of many domestic wells should be reduced in order to delay the significant water quality degradation and the reduced pumped quantity to be compensated by drilling new wells in selected areas. Commitment to PWA recommendation in terms of pumping rate for each well. Gaza strip cannot continue depending on the groundwater as the only source to cover their water needs for all purposes where new water resources such as seawater desalination and reclaim of wastewater use. The water quality will be worse in the next few years and the aquifer will not be able to cover the people water needs, where the water quality will not able to be used for any purposes (domestic, agriculture, ). 13