Conjunctive surface water and groundwater modeling for sustainable use in Colorado River Delta using MODFLOW, México [recurso electrónico] / Kedir Mohammed Bushira ; director, Jorge Ramírez Hernández

Maestría y Doctorado en Ciencias e Ingeniería.

Tesis (Doctorado) --Universidad Autónoma de Baja California. Instituto de Ingeniería, Mexicali, 2018.

Incluye referencias bibliográficas.

The Mexicali valley in Colorado River delta has been one of the most productive agricultural regions in the area. The valley also is rapidly becoming an important area for Baja California's expanding urban population. Quantification of groundwater flow dynamics and groundwater flow components represent a key component for a development of better water management strategies. This paper is aimed to simulate the groundwater flow dynamics and groundwater flow components of the Mexicali Valley aquifer for better water management strategies by applying a hydrological conceptual model into an integrated hydrological numerical model. The numerical model was developed using the MODFLOW-OWHM code under the ModelMuse Graphical User Interface, where the surface-groundwater interactions through unsaturated zone were simulated using the River Package (RIV) and Unsaturated-Zone Flow (UZF1) MODFLOW packages. A conceptual model was developed to simulate the groundwater flow and to estimate groundwater balance components from 2002 to 2010 stress periods. After reasonable calibration on the most uncertain parameters (Horizontal hydraulic conductivity and specific yield), the model produced a general view of the groundwater fluxes in the study area and generated insights into the groundwater balance components in the study period. A steady-state model was calibrated using 27 observation wells of average hydraulic heads and the transient simulation was calibrated using 45 observation wells. In the steady-state calibration, gross recharge, contributed 93.3%, lateral inflow 3.2% and stream leakage 3.4% of the total groundwater inflow. The groundwater outflow consisted of groundwater evapotranspiration 87.5%, surface leakage 3.1%, groundwater pumping 3.09% and lateral outflow 6.31%.
In the transient model simulation, the water budget components that contributed to the groundwater input were: gross recharge (34.35%) and lateral inflow (65.64%). The discharges that contributed to the groundwater output were: pumping (45.61%), groundwater evapotranspiration (8.9%), outflow through drain (12.66%), lateral outflow (21.58%), groundwater exfiltration (10.81 %), leakage from groundwater to streams (0.44 %), and storage change (Δs) of -19.91 x 106 m3.
The calibrated transient model showed temporally and spatially variable patterns of groundwater fluxes. The groundwater evapotranspiration (ETg) ranged from -40.2
MODFLOW Modeling Colorado River Delta
v
Mm3year-1 at the end of the transient modeling period to -100.4 Mm3 year-1 in the year 2004 with an average of – 78.32 Mm3 year-1; the groundwater exfiltration (Exfgw) ranged from 93.5 Mm3 year-1 in 2003 to 104.4 Mm3 year-1 in the year 2008 with an average of 94.9 Mm3 year-1; The calculated net recharge was ranged from 95.8 Mm3 year-1 to 212.2 Mm3 year-1.
Processes encountered in the calibrated parameterizations show groundwater flows axially from almost all directions of the model towards the Gulf of California at the south border of the model, match the course of the Colorado River and laterally towards the new river in the North-west, with a larger portion flowing out Southward than North-westward. The numerical modeling results showed that if the irrigation demands continue to increase, the current situation would lead to an acceleration of the groundwater depletion which might introduce ecological problems to the study area. Overall, the model provides a detailed MODFLOW analysis of changes in groundwater availability.