Water Resources Assessment

• Main Resources– Surface water– Groundwater– Unconventional

• Tools– Flood routing/delineation models– Runoff models– GIS– Finite element – Finite difference– Lumped parameters models

Surface Water

• General Equation

I(t) – O(t) = ΔS/Δt• Oin Inputs

– Precipitation– Base flow

• Oin Outputs– E/ET– Infiltration– Intakes

Qin

Qout

S

System Boundaries

• Reservoir– Balance

ΔS/Δt=(P*Ares+Qin)-(E*Ares+Qout)

– Residence Time

S/I(t)

• Watershed ΔS/Δt=(P*A)-(ET*A+Qout)

Groundwater

• Definitions– Saturated Zone: VWater=Vvoids– Unsaturated Zone: VWater < Vvoids– Moisture Content: VWater < Vtotal– Voids/Pores: allow the flow of water– Water Table: surface where the water pressure in the pores

equals Zero– Porosity: n = Vvoids / Vtotal (~0 - 0.7)– Hydraulic conductivity [L/T]= represents how easily water can

flow through formation• Gravel >50 m/day• Course Sand: K = 30-50 m/day• Fine sand: K = 10-30 m/day• Silt: K = 1-10 m/day• Clay: K < 1 m/day

Groundwater

• Definitions– Formations types with respect to water bearing

• Aquifer = permeable layer that contains and transmits water in large quantities

– Confined– Unconfined

• Aquiclude = impermeable layer that may contain water but transmissivity is very low

• Aquitard = semi permeable layer that transmits water in the vertical direction only

• Aquifuge = impermeable layer that neither contains nor transmits water

General Cross Section of Gaza Aquifer

calcareous sandstone, unconsolidated sands

Eocene chalks and limestone

Clay

marls, marine shales, and claystones

Groundwater

– Darcy

Adl

dhKQ

dl

dhKvq

g

pzh

gCd

K2

Intrinsic permeability

Groundwater

– Average pore velocity

– Problem: A tracer traveled 3 days and 6 hours between 2 wells

that are 20 m apart. Water elevation difference between the wells is 0.5m, porosity n=0.15. Estimate v, q, K

dl

dhKq

n

qv

Groundwater Balance

dl

dhKq

dt

dS

dz

dhK

dz

d

dy

dhK

dy

d

dx

dhK

dx

dzyx

dt

dhS

dz

dhK

dz

d

dy

dhK

dy

d

dx

dhK

dx

dszyx

Ss [1/L] = Specific Storage = volume of water that a unit volume of aquifer releases under a unit decline in hydraulic headS [dimensionless] = Storativity = volume of water that a unit surface area of aquifer releases under a unit decline in hydraulic head

Groundwater Balance

• Pollutants transport mechanisms– Advection– Diffusion– Dispersion

*DvDl dt

dC

dl

dCv

dl

CdD

dx

dll

2

2

Mechanical dispersion coefficient Diffusion coefficient

Average Nitrates Concentrations (PWA, 2005 Data)

Average Chlorides Concentrations (PWA, 2005 Data)

0

12

-1

3

4

-2

5

6

-3

-4

7

-5

8

-6

9-8

-7 -9 10-10

-4

2

1

-3

0

-1

1

0

2

-1

0

0

-2

-4

Gaza StripGroundwater Level Contours (m)

0 2 4 6 Kilometers

N

EW

S

Average Groundwater Level (PWA, 2005 Data)

Gaza Strip

Soil TypeDark brown / reddish brownLoess soilsLoessal sandy soilSandy loess soilSandy loess soil over loessSandy regosols

Soil Map

Gaza StripBuiltup AreasLocal roads.shp

Built Up Areas

Gaza Strip

All crops.shpAlmondsCitrusCitrus mixed witDatesGrapesGreenhousesHorticultureOlivesRainfed Crops

Agricultural Areas