Spatial distribution of δ2H and δ18O values in the hydrologic cycle of the Nile Basin
Jeff B LANGMAN1,2
1 School of Science and Engineering, American University in Cairo, Cairo 11835, Egypt; 2 Department of Geological Sciences, University of Idaho, Moscow 83844, USA
Spatial distribution of δ2H and δ18O values in the hydrologic cycle of the Nile Basin
Jeff B LANGMAN1,2
1 School of Science and Engineering, American University in Cairo, Cairo 11835, Egypt; 2 Department of Geological Sciences, University of Idaho, Moscow 83844, USA
摘要 Existing δ2H and δ18O values for precipitation and surface water in the Nile Basin were used to analyze precipitation inputs and the influence of evaporation on the isotopic signal of the Nile River and its tributaries. The goal of the data analysis was to better understand basin processes that influence seasonal streamflow for the source waters of the Nile River, because climate and hydrologic models have continued to produce high uncertainty in the prediction of precipitation and streamflow in the Nile Basin. An evaluation of differences in precipitation δ2H and δ18O values through linear regression and distribution analysis indicate variation by region and season in the isotopic signal of precipitation across the Nile Basin. The White Nile Basin receives precipitation with a more depleted isotopic signal compared to the Blue Nile Basin. The hot temperatures of the Sahelian spring produce a greater evaporation signal in the precipitation isotope distribution compared to precipitation in the Sahara/Mediterranean region, which can be influenced by storms moving in from the Mediterranean Sea. The larger evaporative effect is reversed for the two regions in summer because of the cooling of the Sahel from inflow of Indian Ocean monsoon moisture that predominantly influences the climate of the Blue Nile Basin. The regional precipitation isotopic signals convey to each region’s streamflow, which is further modified by additional evaporation according to the local climate. Isotope ratios for White Nile streamflow are significantly altered by evaporation in the Sudd, but this isotopic signal is minimized for streamflow in the Nile River during the winter, spring and summer seasons because of the flow dominance of the Blue Nile. During fall, the contribution from the White Nile may exceed that of the Blue Nile, and the heavier isotopic signal of the White Nile becomes apparent. The variation in climatic conditions of the Nile River Basin provides a means of identifying mechanistic processes through changes in isotope ratios of hydrogen and oxygen, which have utility for separating precipitation origin and the effect of evaporation during seasonal periods. The existing isotope record for precipitation and streamflow in the Nile Basin can be used to evaluate predicted streamflow in the Nile River from a changing climate that is expected to induce further changes in precipitation patterns across the Nile Basin.
Abstract: Existing δ2H and δ18O values for precipitation and surface water in the Nile Basin were used to analyze precipitation inputs and the influence of evaporation on the isotopic signal of the Nile River and its tributaries. The goal of the data analysis was to better understand basin processes that influence seasonal streamflow for the source waters of the Nile River, because climate and hydrologic models have continued to produce high uncertainty in the prediction of precipitation and streamflow in the Nile Basin. An evaluation of differences in precipitation δ2H and δ18O values through linear regression and distribution analysis indicate variation by region and season in the isotopic signal of precipitation across the Nile Basin. The White Nile Basin receives precipitation with a more depleted isotopic signal compared to the Blue Nile Basin. The hot temperatures of the Sahelian spring produce a greater evaporation signal in the precipitation isotope distribution compared to precipitation in the Sahara/Mediterranean region, which can be influenced by storms moving in from the Mediterranean Sea. The larger evaporative effect is reversed for the two regions in summer because of the cooling of the Sahel from inflow of Indian Ocean monsoon moisture that predominantly influences the climate of the Blue Nile Basin. The regional precipitation isotopic signals convey to each region’s streamflow, which is further modified by additional evaporation according to the local climate. Isotope ratios for White Nile streamflow are significantly altered by evaporation in the Sudd, but this isotopic signal is minimized for streamflow in the Nile River during the winter, spring and summer seasons because of the flow dominance of the Blue Nile. During fall, the contribution from the White Nile may exceed that of the Blue Nile, and the heavier isotopic signal of the White Nile becomes apparent. The variation in climatic conditions of the Nile River Basin provides a means of identifying mechanistic processes through changes in isotope ratios of hydrogen and oxygen, which have utility for separating precipitation origin and the effect of evaporation during seasonal periods. The existing isotope record for precipitation and streamflow in the Nile Basin can be used to evaluate predicted streamflow in the Nile River from a changing climate that is expected to induce further changes in precipitation patterns across the Nile Basin.
Jeff B LANGMAN. Spatial distribution of δ2H and δ18O values in the hydrologic cycle of the Nile Basin[J]. 干旱区科学, 2015, 7(2): 133-145.
Jeff B LANGMAN. Spatial distribution of δ2H and δ18O values in the hydrologic cycle of the Nile Basin. Journal of Arid Land, 2015, 7(2): 133-145.
Abu-Zeid M A, El-Shibini F Z. 1997. Egypt’s High Aswan Dam. International Journal of Water Resources Development, 13(2): 209–218. Amarasekera K N, Lee R F, Williams ER, et al. 1997. ENSO and the natural variability in the flow of tropical rivers. Journal of Hydrology, 200: 24–39.Awadallah A G, Rousselle J. 2000. Improving forecasts of Nile flood using SST inputs in TFN model. Journal of Hydrologic Engineering, 5(4): 371–379.Beyene T, Lettenmaier D P, Kabat P. 2010. Hydrologic impacts of climate change on the Nile River Basin—implications of the 2007 IPCC climate scenarios. Climatic Change, 100 (3/4): 433–461.Booij M J, Tollenaar D, van Beek E, et al. 2011. Simulating impacts of climate change on river discharges in the Nile Basin. Physics and Chemistry of the Earth, Parts A/B/C, 36(13): 696–709. Buontempo C, Lørup J K, Antar M A, et al. 2009. Assessing the impacts of climate change on the water resources in the Nile Basin using a regional climate model ensemble. In: Climate Change and Water Systems: Global Risks, Challenges & Decisions. Copenhagen: Earth and Environmental Science IOP Conference Series, 6(29).Camberlin P. 1997. Rainfall anomalies in the source region of the Nile and their connection with the Indian summer monsoon. Journal of Climate, 10(6): 1380–1392. Conway D. 2005. From headwater tributaries to international river: observing and adapting to climate variability and change in the Nile Basin. Global Environmental Change, 15(2): 99–114. Conway D, Hulme M. 1996. The impacts of climate variability and future climate change in the Nile Basin on water resources in Egypt. International Journal of Water Resources Development, 12(3): 277–296. Conway D, Krol M, Alcamo J, et al. 1996. Future availability of water in Egypt: the interaction of global, regional, and basin scale driving forces in the Nile Basin. Ambio, 25(5): 336–342.Craig H. 1961. Isotopic variations in meteoric waters. Science, 133: 1702–1703.Craig H, Gordon L I. 1965. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In: Lishi V, Pisa F. Proceedings of Stable Isotopes in Oceanographic Studies and Paleotemperatures. Spoleto, Italy: Geologic Nuclear Laboratory, 9–130. Dansgaard W. 1964. Stable isotopes in precipitation. Tellus, 16: 436–468.El-Asrag A M. 2005. Effect of synoptic and climatic situations on fractionation of stable isotopes in rainwater over Egypt and east Mediterranean. In: International Atomic Energy Agency, Isotopic Composition of Precipitation in the Mediterranean Basin in Relation to Air Circulation Patterns and Climate, IAEA-TECDOC-1453. Vienna, Austria, 51–73.Eldaw A K, Salas J D, Garcia L A. 2003. Long-range forecasting of the Nile River flows using climatic forcing. Journal of Applied Meteorology, 42: 890–904.Elshamy M E. 2009. Assessing the hydrological performance of the Nile Forecast System in long-term simulations. Nile Water Science & Engineering Journal, 1(3): 22–40.Elshamy M E, Seierstad I A, Sorteberg A. 2009. Impacts of climate change on Blue Nile flows using bias-corrected GCM scenarios. Hydrology and Earth System Sciences, 13: 551–565.Eltahir E A B. 1996. El Niño and the natural variability in the flow of the Nile River. Water Resources Research, 32(1): 131–137.Gat J R, Carmi I. 1970. Evolution of the isotopic composition of atmospheric waters in the Mediterranean Sea area. Journal of Geophysical Research, 75(15): 3039–3048. Gat J R, Dansgaard W. 1972. Stable isotope survey of the fresh water occurrences in Israel and the northern Jordan Rift Valley. Journal of Hydrology, 16(3): 177–211.Gat J R. 2001. Atmospheric waters. In: Mook W G. Environmental Isotopes in the Hydrologic Cycle: Principles and Applications. Technical Documents in Hydrology, Vol. II. UNESCO, Paris, No. 39.Gat J R, Klein B, Kushnir Y, et al. 2003. Isotope composition of air moisture over the Mediterranean Sea: an index of the air–sea interaction pattern. Tellus B, 55(5): 953–965.Gleick P H. 1991. The vulnerability of runoff in the Nile Basin to climatic changes. The Environmental Professional, 13: 66–73.Gonfiantini R, Fröhlich K, Araguas-Araguas L, et al. 1998. Chapter 7: isotopes in groundwater hydrology. In: Kendall C, McDonnell J J. Isotope Tracers in Catchment Hydrology. Amsterdam: Elsevier Science B.V., 203–246.Guichard F, Kergoat L, Mougin E, et al. 2009. Surface thermodynamics and radiative budget in the Sahelian Gourma—seasonal and diurnal cycles. Journal of Hydrology, 375: 161–177. Hoffmann G, Jouzel J, Masson V. 2000. Stable water isotopes in atmospheric general circulation models. Hydrological Processes, 14: 1385–1406.Hulme M. 1994. Global climate change and the Nile Basin. In: Howell P P, Allan J A. The Nile: Sharing a Scarce Resource. Cambridge: Cambridge University Press, 139–162.Hulme M, Doherty R, Ngara T, et al. 2001. African climate change: 1900–2100. Climate Research, 17(2): 145–168.International Atomic Energy Agency (IAEA). 2005. Summary. In: International Atomic Energy Agency, Isotopic Composition of Precipitation in the Mediterranean Basin in Relation to Air Circulation Patterns and Climate. Vienna: International Atomic Energy Agency, IAEA-TECDOC-1453, 1–5. International Atomic Energy Agency (IAEA). 2014. Global Network of Isotopes in Precipitation (GNIP). International Atomic Energy Agency, Water Resources Programme, Vienna. http://www-naweb. iaea.org/napc/ih/IHS_resources_gnip.html.Johnson P A, Curtis P D. 1994. Water balance of Blue Nile River Basin in Ethiopia. Journal of Irrigation and Drainage Engineering, 120(3): 573–590.Liotta M, Favara R, Valenza M. 2006. Isotopic composition of the precipitations in the central Mediterranean: origin marks and orographic precipitation effects. Journal of Geophysical Research: Atmospheres, 111(D19): 2156–2202.Mathieu R, Pollard D, Cole J E, et al. 2002. Simulation of stable water isotope variations by the GENESIS GCM for modern conditions. Journal of Geophysical Research, 107(D4): 1–18.Merlivat L, Jouzel J. 1979. Global climatic interpretation of the deuterium-oxygen 18 relationship for precipitation. Journal of Geophysical Research, 84(C8): 5029–5033.Nicholson S E. 1994. Desertification. In: Schneider S H. Encyclopedia of Climate and Weather. New York: Oxford University Press, 239–242.Noone D, Simmonds I. 2002. Associations between delta O-18 of water and climate parameters in a simulation of atmospheric circulation for 1979–95. Journal of Climate, 15: 3150–3169.Poage M A, Chamberlain C P. 2001. Empirical relationships between elevation and the stable isotope composition of precipitation and surface waters: considerations for studies of paleoelevation change. American Journal of Science, 301: 1–15.Quinn W H. 1992. A study of Southern Oscillation-related climatic activity for A.D. 622–1900 incorporating Nile River flood data. In: Diaz H F, Markgraf V. El Nino: Historical and Paleoclimatic Aspects of the Southern Oscillation. Cambridge, U.K.: Cambridge University Press, 119–149.Risi C, Bony S, Vimeux F, et al. 2010. Understanding the Sahelian water budget through the isotopic composition of water vapor and precipitation. Journal of Geophysical Research, 115, D24110. Rozanski K, Araguás-Araguás L, Gonfiantini R. 1993. Isotopic patterns in modern global precipitation. In: Swart P K, Lohmann K C, McKenzie J, et al. Climate Change in Continental Isotopic Records. Washington, D.C.: American Geophysical Union, Geophysical Monograph Series, 78: 1–36.Sestini G. 1993. Implications of climate change for the Nile Delta. In: Sestini G. Climatic Change in the Mediterranean. London: Edward Arnold Publisher, 535–601.Seleshi Y, Zanke U. 2004. Recent changes in rainfall and rainy days in Ethiopia. International Journal of Climatology, 24(8): 973–983.Strzepek K, Yates D, Yohe G, et al. 2001. Constructing ‘not implausible’ climate and economic scenarios for Egypt. Integrated Assessment, 2(3): 139–157.Sturm K, Hoffmann G, Langmann B, et al. 2005. Simulation of δ18O in precipitation by the regional circulation model REMOiso. Hydrological Processes, 19: 3425–3444.Sun L, Fredrick H M, Semazzi F G, et al. 1999. Application of the NCAR Regional Climate Model to eastern Africa: simulation of interannual variability of short rains. Journal of Geophysical Research: Atmospheres, 104(D6): 6549–6562.Vörösmarty C J, Fekete B, Tucker B A. 1998. River discharge database, version 1.1 (RivDIS v1.0 supplement). Institute for the Study of Earth, Oceans, and Space/University of New Hampshire, Durham NH, USA.Whetton P, Rutherfurd I. 1994. Historical ENSO teleconnections in the eastern hemisphere. Climatic Change, 28(3): 221–253.Yates D N, Strzepek K M. 1998. Modeling the Nile Basin under climatic change. Journal of Hydrologic Engineering, 3(2): 98–108.
2015, Vol. 7 
