Research Article the Hydrogeochemical Stratigraphy of Brines and Its Implications on Water Management in the Central Jordan-Dead Sea Rift Valley, Israel
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Hindawi Geofluids Volume 2020, Article ID 9812597, 17 pages https://doi.org/10.1155/2020/9812597 Research Article The Hydrogeochemical Stratigraphy of Brines and Its Implications on Water Management in the Central Jordan-Dead Sea Rift Valley, Israel Eliahu Rosenthal ,1 Peter Möller,2 Orna Buch-Leviatan ,3 and Moshe Politi3† 1The School of Geosciences, Tel Aviv University, Tel Aviv, Israel 2Helmholtz Centre, German Research Centre for Geosciences, GFZ, Section 3.4, Potsdam, Germany 3Zion Oil and Gas, Inc., Caesarea Industrial Park, Israel † Deceased Correspondence should be addressed to Eliahu Rosenthal; [email protected] Received 5 October 2019; Revised 31 October 2020; Accepted 25 November 2020; Published 17 December 2020 Academic Editor: Mercè Corbella Copyright © 2020 Eliahu Rosenthal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The exploratory borehole Megiddo-Jezre’el 1 (MJ1) was drilled in Israel, in the Bet She’an Valley which branches out from the Central Jordan Rift. It reached the depth of 5060 m and bottomed within the Upper Triassic Mohilla Fm. Following the increase of groundwater exploitation, the Cl- concentrations increased and ionic ratios changed indicating inflow of Ca2+-Cl- brines, the origins of which were hitherto unknown. Data from the new MJ1 borehole revealed that rock porosities decrease with depth. Lowermost values of about 3% were interpreted from logs in Lower Jurassic and Triassic strata. The highest shut-in pressures were measured in the Upper Jurassic sequence raising the water much higher than the ground surface. Along the drilled section, there is a continuous downward increase in Cl- concentrations in the range of 12-186 g Cl-/l and a very clear stratification of brines. Data from the MJ1 borehole and from other exploration wells indicate that in the subsurface of the area, there are two definite source brines: Triassic brine and the Late Tertiary (so-called) Rift brine. Brines encountered in Jurassic and Cretaceous beds represent ancient mixtures of the two source brines involving various water-rock chemical transformations. Evidence of very high pressures in deep boreholes Devora 2A, Rosh Pinna 1, and MJ1 revealed the existence of a mechanism in which the deep brines are “piston-driven” upwards and possibly also laterally. The ongoing salinization of groundwater in the area is due to the inflow of the Late Tertiary Ca2+-Cl- Rift brines and not that of the Jurassic or Triassic brines. The hydrogeological and hydrochemical data from borehole MJ1 is of major importance for the management of groundwater resources in the Central Jordan Rift Valley and in the adjacent geologically connected areas. 1. Introduction in the Rift and in branched-out areas, intensive exploitation of fresh groundwater has disturbed the natural equilibrium One of the major causes of the water crisis in Israel is the which prevailed between freshwater and saline water. The ongoing contamination of its groundwater resources by newly established groundwater flow regimes have facilitated saline water bodies. The main deteriorating process occur- the further migration of saline groundwater bodies, their par- ring in groundwaters of the Jordan-Dead Sea Rift Valley ticipation in the active hydrological cycle, and the progressive and in adjacent connected areas is the upflow and migration contamination of fresh groundwater [2]. These processes of highly pressurized thermal Ca-chloride brines penetrating were not anticipated by planners and water resources man- into fresh groundwater bodies [1]. In Israel, and particularly agers because there was no sufficient information about the 2 Geofluids occurrence and the physical regimes controlling the migra- (iii) Neogene-Tertiary brines with Ca2+ >Mg2+ encoun- tion of the brines. tered in Tiberias Hot Springs and beyond the Bet A common feature of all groundwater bodies flowing in She’an basin the Jordan-Dead Sea Rift Valley is that these are mixtures + - of low salinity or freshwater bodies with a Ca2+-Cl- saline brine, (iv) Neogene to recent ablation brine with Na /Cl of otherwise known as the “Rift brine.” The origin of the low- about 1 encountered in the deep well Zemah 1 salinity component may differ. South of the Dead Sea, it is usu- located at the southern tip of Lake Tiberias ally the Lower Cretaceous paleowater from the so-called (v) Deep-seated brines of the (Ca, Mg)Cl2 type which “Nubian sandstone aquifer” or recent floodwaters. Further are the subject of the present study northwards, the low-salinity component originates from the Cretaceous (Cenomanian-Turonian) and Tertiary (Eocene) groundwaters. 2. Objects of Investigations 2+ - “ ” The saline Ca -Cl component, i.e., the Rift brine [3], As the result of the ongoing increase of groundwater exploi- fi is identi ed by its high salinity and by typical ionic ratios tation in the Bet She’an and Harod Valleys since the early Q ð + − : 2+ 2+ such as =Ca/ SO4 + HCO3 >1,Na /Cl <08, Mg /Ca 1950s, the chemical composition of the exploited water chan- : − − ≪ Þ - <05, and Cl /Br 286 [4]. Traditionally, Cl /Br is given ged due to variously diluted Ca2+-Cl- brines rising from as a weight ratio, whereas all the other ratios are calculated depths and replacing the fresh groundwater. This process from meq/l values. The brine is characterized by high pres- and its chemical details are similar for all water resources in sures and elevated temperatures and is encountered mainly the Rift, from Lake Kinneret in the north to the Arava in (but not exclusively) along the western margins of the Rift, the south. In all these areas, scholars asked the same ques- from the region of Lake Tiberias in the north to the northern tions which remained equally unanswered because of a lack Arava in the south. The chemical evolution was characterized 2+ of information from horizons deeper than 800 m. These by the increase of the Ca concentrations as indicated by the questions are as follows: raise of the Q value to values of ≫1, decrease of the Na+/Cl- to - - values of <0.7, and Cl /Br decrease to values much lower (i) Is there only one upflowing brine or are there several than 286. All these chemical changes are clearly indicative brines of similar composition but generated in dif- 2+ - of progressive inflow of pressurized and thermal Ca -Cl ferent rock units and on different occasions? brines which are encountered in the Jordan Rift Valley and in the adjacent areas which are in structural contact with (ii) What are the chemical compositions of the subsur- the Rift [5]. face brine(s)? fi Two types of brines were identi ed in the Rift [3]): (iii) In which rock units were these brines generated? (i) Predominantly phreatic and nonthermal saline (iv) What is their updriving mechanism and at what groundwater with Mg2+/Ca2+ >1 occurs along rate? the eastern and southeastern shores of Lake (v) At what depth do the different brine bodies occur? Tiberias (vi) Assuming that answers are available to these ques- (ii) Pressurized, thermal, and saline groundwater with tions, what would be the impact of upflowing brines equivalent ratios of Mg2+/Ca2+ <1 occurs mostly on future regional plans for water exploitation? along the western margins of the Rift, between Lake Tiberias in the north and the Arava Valley in the The recent drilling of the deep exploratory borehole 2+ - far south. Freshwater-diluted Ca -Cl brines mostly Megiddo-Jezre’el 1 (MJ1) supplied answers to many of the ascend near fault escarpments [1] abovementioned questions. The present paper summarizes the results and their contribution to the understanding of The study of groundwater salinization in the Rift started the genesis and movement of brines in the Rift and in the in the early 1960s [3]. Numerous researchers suggested a structurally connected regions. wide range of geological scenarios [6, 7]. Considering chemical and stable isotope data, it occurs that the water bodies contributing to saline groundwater in 3. Materials and Methodology the Rift are as follows [6]: The present study is based on the geological evidence from (i) Recent Dead Sea water which is a primary evapora- the recently drilled deep (5060 m) exploratory borehole ’ tion brine with high Mg2+ >Ca2+ Megiddo-Jezre el 1 (MJ1), located 800 m south of Kibbutz Sde Eliahu, in the Bet She’an Valley, at Israeli coordinates (ii) Neogene seawater evaporation brine in the 248240/703782, and Kelly Bushing (KB) at -180.1 m bsl. flooded Rift as represented by the Ha’On saline Until then, subsurface geological information in the area water characterized by Mg2+ >Ca2+. This saline was limited only to the western and southern margins of water flows out from springs and seepages along the Bet She’an Valley, where it was derived from water wells the eastern and southeastern shores of Lake such as Revaya 1-7, Bardala 1-2, and Mehola 5 (Cretaceous Tiberias Judea Group aquifer) (Figure 1) [8]. The depths of these Geofluids 3 35.45 35.5 35.55 Geological legend .55 Bc - Pliocene Cover Basalt 32 Bm - Miocene Lower Basalt Blc - Lower Cretaceous Tayasir Volc. q - Holocene ql,qt - Quaternary p - Pliocene Bira Fm. nqc - Neogene-Quaternary m - Miocene Hordos Fm. and Um Sabune Fm. et,ebk - Eocene Avedat Gr. s p - Senonian Mt. Scopus Gr. t - Turonian Judea Gr. .5 32 c1,c2,c3 - Up. Cretaceous Judea Gr. lck - Low. Cretaceous Kurnub Gr. lc - Low. Cretaceous ju- Up.J urassic Arad Gr. Fm - Formation Gr - Group Oil well .45 32 34.4 34.6 34.8 35 35.2 35.4 35.6 33 Rosh Pinna1 .8 32 Atlit 1 deep Deborah 2A .6 32 MJ1 .4 32 Gaash 1 Gaash 2 .4 .2 Meged 4 32 Meged 2 32 32 .8 31 .6 31 .4 Gerar 1 31 Beeri 1 .2 Hazerim 1 Zavoa 1 Shezaf 1 31 31 Sherif 1 Qeren 1 a .35 .8 Avdat 1 Kurnub 1 32 30 Nafa .6 Ramon 1 30 .4 012km 30 02040km Sources: Esri, USGS, NOAA Figure 1: Geological location map.