Modeling regional salinization of the Ogallala aquifer, Southern High Plains, TX, USA

Abstract

Two extensive plumes (combined area Ͼ1000 km 2 ) have been delineated within the Ogallala aquifer in the Southern High Plains, TX, USA. Salinity varies within the plumes spatially and increases with depth; Cl ranges from 50 to Ͼ500 mg l Ϫ1. Variable-density flow modeling using SUTRA has identified three broad regions of upward cross-formational flow from the underlying evaporite units. The upward discharge within the modeled plume area is in the range of 10 Ϫ4 -10 Ϫ5 m 3 day Ϫ1 , and the TDS concentrations are typically Ͼ3000 mg l Ϫ1. Regions of increased salinity, identified within the Whitehorse Group (evaporite unit) underlying the Ogallala aquifer, are controlled by the structure and thickness variations relative to the recharge areas. Distinct flow paths, on the order of tens of km to Ͼ100 km in length, and varying flow velocities indicate that the salinization of the Ogallala aquifer has been a slow, ongoing process and may represent circulation of waters recharged during Pleistocene or earlier times. On-going pumping has had negligible impact on the salinity distribution in the Ogallala aquifer, although simulations indicate that the velocity distribution in the underlying units may have been affected to depths of 150 m after 30 years of pumping. Because the distribution of saline ground water in this region of the Ogallala aquifer is heterogeneous, careful areal and vertical characterization is warranted prior to any well-field development. ᭧

Simulating Temporal and Spatial Changes of Soil Salinity in Yellow River Delta, China Using GIS

“…79% of testing samples had relative error under 20% for (11), 73% of testing samples for (6) and (7), and 58% of testing samples for (9) and (10). That is to say, (3), (4), (5), and (8) have high precision, (6), (7), and (11) moderate precision, and (9) and (10) low precision comparatively. Figure 1 was dynamic of the simulated soil salinity at the end of the months from May to October.…”

“…The variables are same with following equations. Equation (6) is the model to simulate salinization for salinic fluvo-aqui soil in May and June, (7) in July and August, and (8) Salinization predicting models of fluvo-aqui soil are formed as (9), (10), and (11) and they are adapted for time from May to June, July to August, and September to October respectively. SS = 1.084 SS t-1 +2.739*10 -2 d t-1 -2.169 ECw t-1 -4.883*10 -3 P + 3.995*10 -3 E +1.837 (9) SS = 0.937 SS t-1 -6.270*10 -2 d t-1 -2.818*10 -2 ECw t-1 -1.321*10 -3 P +1.518*10 -2 E -0.115 (10) SS = 0.968 SS t-1 -5.795*10 -2 d t-1 -0.316 ECw t-1 -2.086*10 -3 P -4.327*10 -3 E + 0.534 (11) Those equations were derived from multiple linear regressions.…”

“…Qualitative analysis for predicting soil salinity, which are based on experience and knowledge of expert, does not meet demand of precise prediction. Deduced form mechanism or pedo-transfer functions (PTFs), several mathematic models were developed to predict the soil salinity [4][5][6][7][8]. With the computer and modern special information technologies development, models were integrated with geographic information system (GIS) and remote sensing (RS) to simulate regional soil salinity recently [9][10][11][12][13].…”

Previous and Current Status of Groundwater Salinity in East of Blue Nile Communities of Sudan

“…The intersect between the high-andlow TDS end-members are generally observed in areas of high discharge or in an area adjacent to seawater, due to replacement control activities. The salinity is a result of cross-formational flow underling evaporite units; increased salinity is attributed to natural cross-formational discharge along distinct flow paths as influenced by topography (Mehta et al, 2000).…”

“…Groundwater found in such areas can be extremely high in minerals such as sodium, sulfate and chlorides (Mehta et al, 2000). Abundant recharge from low TDS precipitation and longtime dissolution of the unconsolidated sediments containing small amount of soluble compositions lead to low TDS of the groundwater (Ali, 2005).…”