Alluvial fans formed from sediments derived from erosion of the Juárez Mountains in northernmost México have a significant flood impact on the Ciudad Juárez, which is built on the fan system. The northern part of Ciudad Juárez is the most active; further south, older parts of the fan, upon which the rest of the city is built, were largely eroded by natural processes prior to human habitation and subsequently modified only recently by human construction. Three aeolian sand samples, collected from the uppermost (youngest) parts of the fan system in the city area, in places where human intervention has not disturbed the sediment, and constrain the latest dates of fan building. Depositional ages of the Quaternary alluvial fans were measured using Optically Stimulated Luminescence (OSL) on aeolian sands that have inter-fingered with alluvial fan material. These dates are: a) sample P1, 31 ka; b) sample P2, 41 ka; c) sample P3, 74 ka, between Oxygen Isotope Stages (OIS) 3 to 5. They demonstrate that fan development, in the area now occupied by the city, terminated in the Late Pleistocene, immediately after what we interpret to have been an extended period of erosion without further deposition, lasting from the Late Pleistocene to Holocene. The three dates broadly correspond to global glacial periods, implying that the cool, dry periods may reflect periods of aeolian transport in northern México in between phases that were wetter to form the alluvial fans. Alluvial fan margins inter-finger with fluvial terrace sediments derived from the Río Bravo, indicating an additional component of fan dissection by Río Bravo lateral erosion, presumed to be active during earlier times than our OSL ages, but these are not yet dated. Further dating is required to ascertain the controls on the fan and fluvial system.

A Small Perched Perennial Spring has been used for Irrigation for 25 years. With an area of 23.3 ha its water potential basin varies from 90.7 to 979 m3/day so water conductivity of (k=62 cm/day producing between 0.30 to 3.17 lt/sec for lowest to highest rain return period (PR1 to PR100). Water Quantity and Hydraulic conductivity already mentioned were evaluated: Firstly, RPS structure were formed for 100 m of thick impervious lowermost member Lagrima Formation (Kli) overloading for a medium porosity (Klm, Klu) as well as high porosity of Finlay and del Norte Formations (Kf, Kdn). Secondly, Rainfall-Runoff-Recession hydrology model with Recession constant of 0.6 and ratio to pick of 0.2 in the threshold were used trough the simulation. Thus, Base (underground) and Direct (surface) runoff were separated. Finally, water quality and its interaction with host rocks were performed so; two water samples were collected and studied. Both samples were qualified as: Calcic-Bicarbonated (6f-C2) with low salinization risk (C3-S2). Therefore, water could be used for irrigation. In addition, water interaction among Cretaceous rocks of Sierra de Juárez as Lagrima (Kl), Finlay (Kf) and del Norte (Kdn) formations suggests three cases; One; If Calcium reduces Sodium increases given a sodic shale-slate system as: Ca2+HCO3+shales+Na+→Na++HCO3+shales+Ca2, this suggests that water have been confined by rock sourced Cretaceous Lagrima formation (Kli). Two, RPS overloaded recharge layers; Finlay (Kf) and (Kdn) with high karstification potential as high porosity is evident so: Three. If Na+ differ from Cl- thus, the cationic exchange has more Na+ than Cl- so more risk to karstification arises as mentioned before.

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