Isotopic Composition of Rainfall in Baja California Sur, México
Total Page:16
File Type:pdf, Size:1020Kb
International Journal of Hydrology Research Article Open Access Isotopic composition of rainfall in Baja California Sur, México Abstract Volume 5 Issue 3 - 2021 The study of the connection between precipitation and groundwater recharge/discharge Luis González-Hita, Miguel Angel Mejía- using stable isotopes has been limited in México. One of the main limitations is the lack of local stable isotopes monitoring for rainfall. Indeed, only two stations of the Global González, Blanca Carteño-Martinez, Juan Network of Isotopes in Precipitation operated in Mexico from 1962 to 1988. This study Carlos Aparicio-González, Dustin Mañón- reports temporal characterization of stable isotopes in meteoric waters in the northwest of Flores Mexico that has been lacking up to the present. Stable isotope analyses of the rain collected Department of Hydrology, Mexican Institute of Water in the city of Loreto, state of Baja California Sur, from 2018 to 2021 were conducted using Technology, México laser water isotope analyzers Picarro L2110-i and Los Gatos Research LWIA-45EP. A least Miguel Angel Mejía-González, Mexican squares regression of the isotope data was used to obtain the local meteoric water line: Correspondence: Institute of Water Technology, Paseo Cuauhnahuac 8532, δ2H =8 δ18O + 9.4 (r2=0.98). The average value of winter rain is δ18O=-2.46 ‰ and δ2H=- 18 2 18 Jiutepec, Morelos, México, 10.2 ‰, monsoon rain δ O=-4.93 ‰ y δ H=-30.3 ‰, atmospheric river rain δ O=-5.35 Email ‰ and δ2H=-33.3 ‰ and tropical cyclones rain δ18O= -10.7 ‰ y δ2H=-76.3. Isotope data indicated that tropical cyclones are the main source of recharge for the coastal aquifers of Baja California, Sur. Received: April 28, 2021 | Published: June 01, 2021 Keywords: Baja California Sur México, stable isotopes, rainfall, local meteoric water line, national network of isotopes in precipitation Abbreviations: GNIP, global network of isotopes in the other in the city of Veracruz (Gulf of Mexico) from 1962 to 1988. precipitation; IMTA, Mexican institute of water technology; The study of the connection between precipitation and groundwater RENIP, national network of isotopes in precipitation; NPSH, north recharge/discharge using stable isotopes has been limited in México. pacific subtropical high; NAH, north American high; MM, Mexican One of the main limitations is the lack of local stable isotopes monsoon; TS, tropical systems; ARs, atmospheric rivers; TC, tropical monitoring for rainfall. cyclones In order to incorporate isotope hydrology into national water resources assessments, the Mexican Institute of Water Technology Introduction (IMTA) installed in 2018 a National Network of Isotopes in Several researchers have studied the contribution of different Precipitation (RENIP). This paper presents the stable isotopes of atmospheric mechanisms to the precipitation and groundwater oxygen and hydrogen in precipitation, obtained from 2018 to 2021 recharge of the subtropical zones of Mexico. Rodgers1 reports that in the rainwater collector installed in the coastal city of Loreto in the tropical cyclones (TC) contribute 30 to 40 percent of the rainfall of state of Baja California Sur. Results provide temporal characterization Baja California Sur. Jiang2 found that the maximum contribution of of stable isotopes in meteoric waters in the northwest of Mexico that TC in the East-Central Pacific Basin occurs near the coast of Baja has been lacking up to the present. This study may contribute to California Sur (about 55%). Breña-Naranjo3 after analyzing rainfall the understanding of groundwater recharge mechanisms in the arid data from 1998 to 2013, determined that TC contributes with 40% of subtropical regions of Mexico.9,10 the total annual rainfall in Baja California Sur. According to García4 in Baja California Sur the monsoon produces 28.3% of the cloudiness. Study area 5 The state of Baja California Sur is located in the northwest of Eastoe analyzed the isotopic composition of coastal aquifers o in Baja California Sur, finding that coastal groundwater has Mexico, and limits to the north with Baja California (28 N), to the east with the Gulf of California (109 o W), to the south (23o N) and depleted values, which is not common at this latitude at sea level. o 11 Eastoe assumes it is because tropical cyclones are the main source west (115 N), with the Pacific Ocean (Figure 1). The state has 6 a length of 750 km, an average width of 100 km and 2,200 km of of recharge for coastal aquifers. Ouyss carried out a study of the 11 groundwater flow systems and their environmental interactions, in the coastline. The entity is located within a high-pressure subtropical zone, with dry winds descending, which induce a dry and semi- protected area of Valle de Los Círios, Baja California. They found 11 some groundwater samples with depleted heavy isotopes and low Cl warm to hot climate. The central desert is hot and dry, while the content. They considered these results could be produced by modern cape region has a hot, semi-arid steppe climate. Precipitation is very recharge from tropical cyclones. irregular in time and quantity, so almost all surface currents are intermittent. The average annual precipitation in the period 1941- In order to characterize the spatial and temporal variability of the 2000 was 176 mm, with the highest rainfall from July to January.12 stable isotopes of precipitation on a global scale, the International The potential evaporation is approximately 1,500 mm per year.12 The Atomic Energy Agency and the World Meteorological Organization, most relevant physiographical characteristics are: the Vizcaino Desert implemented the Global Network of Isotopes in Precipitation in the northwest, the plain Llano de Magdalena in the west, and La (GNIP).7,8 The network began operating in 1960, collecting thousands Giganta range in the southeast.13 The mountains to the west are gently of isotope and meteorological data to date. Only two GNIP stations sloping and steep towards the Gulf. operated in Mexico, one in the city of Chihuahua (north Mexico) and Submit Manuscript | http://medcraveonline.com Int J Hydro. 2021;5(3):93‒100. 93 ©2021 González-Hita et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Copyright: Isotopic composition of rainfall in Baja California Sur, México ©2021 González-Hita et al. 94 Figure 1 Study area. Two geomorphological units are distinguished (1) coastal valleys water vapor across the midlatitudes.20 AR are important source of and (2) mountain ranges. The valleys have flat shapes with slight precipitation in many regions, for instance, Dettinger21 estimated that slope to the sea, reduced dimensions and intermittent dense drainage, 25-50% of rainfall in California is produced by AR. The northeast dendritic and subdendritic type in the mountains and parallel in the Pacific is the region where the highest number of AR occurs.22 valleys. The coastal aquifers are unconfined, and consist of alluvial The movement of the NPSH to the north also allows that tropical sediments deposited along the stream courses and on the coastal plain, cyclones (TC) approach to Baja California Sur, reducing atmospheric with small dimensions and little storage capacity.14 Coastal aquifers stability and causing ascending motion that produce deep convection are recharged by direct infiltration of rain over the valleys, as well and precipitation.17 Most of the TC of northeast pacific originate near as by infiltration of runoff in intermittent streams during the rains. the Mexican pacific coast, offshore of the Gulf of Tehuantepec.23 The discharge occurs naturally by groundwater flow to the sea, and Many of the TC turn toward the northwest of México. The states of by evapotranspiration in small areas that have shallow water tables; Baja California Sur and Sinaloa have the highest frequencies of TC artificially it is carried out by the extraction of water in dug and tube touching land in México, both in the northwest.24 wells. Climatic and meteorological characteristics Methodology Among the climatic and meteorological components of the study Monthly precipitation samples were collected from June 2018 to 25,26 area are: North pacific subtropical high (NPSH), North American high January 2021 using a RS2 PALMEX rainwater collector (Figure (NAH), Mexican monsoon (MM), cold fronts, atmospheric rivers and 2) that allows monthly sampling without evaporation or isotopic tropical systems (TS) (cyclones, storms and depressions). The NAH fraction. Samples were filtered using cellulose membranes with 0.45 is a center of high atmospheric pressure (1020 mb) produced in the µm pore size, collected in 60 mL high-density polyethylene bottles winter by low temperatures, in the United States of North America and with conic and polyseal inserts, and filled with no headspace when Canada. Masses of cold and dry air flow from the NAH, causing cold permitted. The collector is located at the facilities of the Loreto fronts in the region.15 Depending on the thermodynamic characteristics National Meteorological Service, CONAGUA, whose coordinates of the environment, the convergence of the cold fronts with low- are (26.011N, 111.35 W) and altitude of 6 m above sea level. level moisture advected from the eastern tropical pacific, produces Rainfall amounts were measured using a Data-Logging Rain Gauge, moderate rain. The NPSH is a center of high atmospheric pressure WatchDog 1120. o (≥1020 mb) in the pacific, located in winter around 28°N,130 W and Stable isotope analyses were conducted at the Isotope Hydrology o o 16 in summer at 38 N,150 W. The NPSH cause intense subsidence and Laboratory of the Mexican Institute of Water Technology (IMTA), atmospheric stability at those latitudes reducing deep convection, using laser water isotope analyzers Picarro L2110-i and Los Gatos 17 which prevents the formation of clouds.