When studying the groundwater flow, one of the main factors that influence its behavior is the topography. Nowadays, we can obtain this topography information from several sources, being GeoTiff,JPG, etc as one of the most popular elevation models format file.you can find the problem and files to download bellow after the video.

VIDEO

The synthetic model is located in the context of a natural alluvial plain in the US Mexico border (Mexico) locally commonly known by irrigation unit 4  and crossed by the Colorado river along Northeastern direction(Yellow line)(Fig.1).

Geographical setting

The hydrological system analyzed is located in an alluvial plain where groundwater and surface water are in hydraulic connection.

Fig1.  Geographical setting and zoom over the study area

Hydro- stratigraphic setup

Three hydro- stratigraphic units (HUs) having flat basal surfaces are identified (Fig2.). From top to bottom:

• an upper sandy unit(HU1), 15m thick, porous, phreatic aquifer
• a silty-clayey unit(HU2)with low permeability,15m thick,acting as an aquitard
• a lower sandy unit(HU3), 15m thick, bounded at the bottom by a massive impervious clayey layer

Fig.2 Hydro stratigraphic setup (vertical cross – section

All model layers are assumed to be hydraulically homogeneous and isotropic,with values of their hydraulic conductivities ( K )shown in the following figure.

Boundary Conditions

The cross border flows along the north boundary of the model domain will be represented by “injection” wells placed in layer 1. A daily rate of 303,938 m³ injected in to into the northern boundary to simulate the 111,013,367 m³ annual seepage toward the aquifer. Assume 10% of the total (11101336.7 m³).

Use a constant head of 100m and 88 m for years 2000 to 2006 and 1996 to 2000 respectively for applying CHD boundary in the northeast and Use a constant  head boundary of  100m from year 2000 to 2006 and 88m from year 1996 to 2000. conductance value were of 0.002 frome the year 1996 to 2000 and 0.03 from the year 2000 to 2006 for GHB in the south.the western boundary is no flow.

Fig.Boundary conditions

Packages

RCH Package: Recharge rate = 3.80E-9, recharge location= Top active cell

EVT Package: EVT Rate = 3.17E-8, EVT surface =Model Top, EVT depth = 0.5, EVT location=Top layer

WELL package: use the attribute table values of the shape file.

Spatial data-sets:  Download them with a single click  using the download link provided bellow

In this MODFLOW Exercise you are provided the following spatial datasets:

A polygon shapefile of the area, called irrigation unit 4.shp

A point shapefile of the groundwater well, called well.shp

A DEM for the model top….

A GHB shape file

A CHD shapefile

Question

Run an annual transient model from 1995 to 2006 by assuming the initial head is equal to the model top and specific storage is 8e-2. Calculates the hydraulic head distribution, a water level and check the budget and investigates the relationships between groundwater and surface-water in terms of water budget.

Input files download link

Irrigation_unit4.shp

ExtractionWells95-06.shp

DEM of the area

CHD-Time variant specified head Package

GHB-General head boundary