PROCESSI DI FLUSSO E TRASPORTO A SCALA DI VERSANTE: SPERIMENTAZIONE DI CAMPO ED ANALISI DELL'INTERAZIONE CON LA FASCIA RIPARIA.

Università degli Studi di Ferrara – Polo Scientifico Tecnologico

La ricerca scientifica italiana nel campo

dell’idraulica:

presentazione dei risultati dei progetti PRIN 2008

Ferrara, 24-25 gennaio 2013

Alberto Bellin1, Alessandra Marzadri2, Daniele Tonina2, Bruno Majone1

1. Dipartimento di Ingegneria Civile, Ambientale e Meccanica, Università degli

Studi di Trento

2. Center for Ecohydraulics Research, University of Idaho, Boise Idaho (USA)

Presentazione dei risultati dei progetti PRIN 2008 - area 08/A1 - 24 e 25 gennaio 2013

Workpackage 1: Sito sperimentale: raccolta, controllo e interpretazione dei dati.

Workpackage 2: Suolo, Analisi locale dell'infiltrazione, bilancio idrico del suolo

Workpackage 4: Interazione versante-canale, ruolo dellafascia riparia

Attività del gruppo di UNITN

� The automated irrigation system serving the orchard canmanage two different watering schedules in two distinctsectors of the field. In these two parts of the orchard (eachone has approximately an area of 1200 m2 with 330 plants)the watering amount and timing are ½ and ¼ of theirrigation schedule adopted by the farmers,1h and 0.5hrespectively.

Maso Maiano experimental site

93.2

N

1514131211109876

5

21

A

A'

3 4

76.5

51.6

7.5

7.7

14

7272

58

2636

925

1013

162411

1417

1215

1822

1920

21

23

3030

1 5

Maso Maiano experimental site (WP1)

z [m] i

0.10 1

0.20 20.30 3

0.50 4

0.80 5

z

∆zi

� Each vertical includes 5volumetric water contentsensors located at differentdepths.

Gateway

Sensor Node

MeshServer

Mobile Terminal

FixedTerminal

Network Architecture

Cooperative Monitoring

Automation: sensing and actuation

Wireless Sensor Network

WSN Deployment

Esperimento in colonna WP2

Nitrogen

Total

BudgetINPUT

GROUNDWATER

Global production of fertilizers (100 TgN/yr) + human sources of reactive N (56 TgN/yr)

OUTPUT

Imbalance ofnitrogen receipts and subsequentlosses to surface waters [Van Breemen et al., 2002].

RIVER

EXPORT

PLANT AND SOIL

Carry about20 TgN/yr morethan 100 years ago

N2O emitted by rivers is estimated as 3 times greater than the IPCC values

SUFFER FOR EXCESSIVE NITROGEN INPUTS

La modellazione del cliclo dell’azoto nei corsi d’acqua

THE HYPORHEIC ZONE (HZ) PLAY AN IMPORTANT ROLE IN PROCESSING DIN AND RETURNING IT TO ATMOSPHERE

ANTHROPOGENIC ACTIVITIES ALTERED THE GLOBAL NITROGEN CYCLE (Increase of DIN)

BIOLOGICAL ACTIVITY WITH NEGATIVE CONSEQUENCES

N2O EMISSIONSSTREAM

EUTROPHICATION

Rivers are hot spots of denitrification

A 3D “pumping”model for hyporheic flows

Our 3D groundwater flow model is an extension of the 2D model developed by Elliott and Brooks (1997) for dune-like bedforms.

(Marzadri et al., WRR 2010)

Solute transport was modeled numerically with the particle tracking technique

0h2 =∇ hnp

Ku ∇⋅−=�

Marzadri & al (WRR, 2010)

Both moments decrease as H*BM increases. Channels With small H*BM have largermoments

TT is lognormally distributed

A 3D “pumping”model for hyporheic flows: Results

Nitrogen is present in the environment in a wide variety of chemical forms that can be grouped in two pools: Organic and Inorganic

Assumptions: • the ratio between carbon and nitrogen (C:N) balanced the processes of mineralization and immobilization and than the NH4

+ can only be depleted by nitrification;• we neglect the DNRA (dissimilatory nitrate reduction to ammonium) reactions, which back transform NO3

- into NH4+

because it was noted by when the ratio of organic carbon and nitrate is high [Storey et al., 2004] and it is assumed to be a minor factor in most stream settings [Duff and Triska, 2000];• we neglect the ANAMMOX reaction occurring during the anaerobic oxidation of NH4+ in N2O because very little is known regarding its existence in surface water biogeochemistry [Kendall et al., 2007].

Nitrogen can be grouped in two pools: Organic and Inorganic

Assumptions: • the ratio between carbon and nitrogen (C:N) balanced the processes of mineralization and immobilization and than the NH4

+ can only be depleted by nitrification;• we neglect the DNRA (dissimilatory nitrate reduction to ammonium) reactions, which back transform NO3

- into NH4+

because it was noted observed when the ratio of organic carbon and nitrate is high [Storey et al., 2004] and it is assumed to be a minor factor in most stream settings [Duff and Triska, 2000];• we neglect the ANAMMOX reaction occurring during the anaerobic oxidation of NH4+ in N2O because very little is known regarding its existence in surface water biogeochemistry [Kendall et al., 2007].

Modeling the transport: a travel time approach

The transport equation for reactive solutes is:

( ) 4,...,0~

2 =+∇∇−∇=∇+∂

∂iperCfCu

u

DCDCu

t

Ciiiiii

i�

�

( )( ) ( )

( )( )

=

=+∂∂

∂∂−

∂∂=

∂∂+

∂∂

∫l

iiiiii

u

d

iperCfCu

u

DCD

C

t

C

0

2

2

4,...,0~

ζζτ

τζζ

ζττ

�

�� ��� ��

Applying mass conservation along a stream tube the previous equation can be written in a more convenient way replacing the space variable with the travel time (τ):

The solutions of this system, according to the initialand boundary conditions, providethe contribution of any stream tube to the transport of i-th quantity Ci

~0

Marzadri et al., WRR 2011

( ) ( )( ) ( )( ) ( ) [ ] ( )( ) ( )( ) ( )

=

=

+−=

−=

−=

tCKtf

tCKtf

tCKKtCKtf

tCKtf

tCKtf

TD

TD

TDTCTN

TN

TRN

,,

,,

,,,

,,

,,

2)(2,4

2)(1,3

2)()(1)(2

1)(1

0)(0

ττττ

τττττ

ττ

NH4+

0=initial concentration of ammonium;DO0= initial concentration of dissolved oxygen; NO3

-0= initial concentration of

nitrate; ; N2O0= initial concentration of nitrous oxide

Nitrification/denitrification reactions and biomass uptake of oxygen and nitrogen are modeled with linearized Monod’s kinetics

Note that the rate constants depend on temperature through the Arrhenius law

A simplified biogeochemical model for DIN

Application

We test our model using the data published by Beaulieu et al (2008, 2009) on theproduction of N2O at a few sites in the Kalamazoo river basin (Michigan USA)

Starting from the hydraulic parameterscharacterizing any site we evaluated theassociated morphodynamic parameterscharacterizing the alternate bar morphology

Q=water dicharge, Y0=mean water depth, U= mean flow velocity, s0= straem slope, d50=mean grain size, ββββ= aspect ratio, θθθθ=Shield stress, ds=relative submergence

Biochemical reaction parameters taken from Beaulieu et al., (2008,2009), Arango and Tank (2008)

Comparison betweenmodel and data of areal production rate of nitrous oxide as a function of stream site location

We can observe that the model captures:

• the areal production of nitrous oxide by the HZ;• the trend of variation of nitrous oxideproduction.

The differences between ourmodel and the data are associable to the fact that:we use the average data;the real value of hydraulicconductivity and pososity are unknown.

Application

Hyporheic zone a sources/sinks for DIN: Ammonium

:

HZ efficiency in removing ammonium versus the Damkhöler Index

HZ is always a sink of NH4

+ irrespective to RC

R1HZ increases with Da because of the longer time available for

nitrification and reaches a constantvalue for Da ≈ 10

03

04

−

+

=NO

NHRC

⇒=

⇒=−=

−

+

3

4

,

,,

2

1with

NOi

NHi

Q

QQR

idwM

iuwM

idwMi

HZ

+

==

lim

0

)()(

lim

50

ln1

)morphologystream(

DO

DO

KK

fDa

TNTR

ττ

Hyporheic zone a sources/sinks for DIN: Ammonium

:

HZ efficiency in removing nitrate versus the Damkhöler Index

R2HZ<0����NH4

+ > NO3- & small

Da: NO3- produced by

nitrification of a NH4+ is larger

than that removed in the anaerobic portion of the HZ (SOURCE)

Das is a particular value of Da, above which theHZ acts as a SINK of NO3

-

03

04

−

+

=NO

NHRC

RHZi =

QM ,dwi −QM ,uw

i

QM ,dwi

withi =1⇒ NH4

+

i = 2⇒ NO3−

Prevailing conditions along the streamline

Conclusions

Our process based model shows that hyporheic zone controls the dynamics of the inorganic nitrogen species:

Implement this model into a catchment scale modeling approach where the stream is one of the geomorphic units in which the catchment is subdivided

Residence time

Temperature

Land use

FUTURE DEVELOPMENTS

A geochemical model for DIN

EGU 2011: HYPORHEIC DISSOLVED OXYGEN AND NITROGEN D YNAMICS IN GRAVEL BED RIVERS – Vienna 6 April 2011

Ammonium C1:

Decreases during nitrification processes, which convert ammonium to nitrate by consuming oxygen

Increases during nitrification processes and decreases during both denitrification processes, which convert nitrate into nitrogen gas and during biomass consuming

Nitrate C2:

Nitrification/denitrification reactions and biomass uptake of oxygen and nitrogen are modeled with linearized Monod’s kinetics

Nitrogen gases(N2+N2O)C3:

Emitted during denitrification processes, which convert nitrate to dinitrogen and nitrous oxide