Design and optimisation of hydrometric networks. Objectives of hydrometric networks 2. Design of hydrometric networks 3. Diagnostic of hydrometric networks 4. Rationalisation and optimisation

Design and

optimisation of

hydrometric

networks

Training module on Hydrological

Expertise and

IWRM

WMO / OMM

Volta-HYCOS Project

IRD -

Unite

OBHI (Observatoires Hydrologiques and Ingenierie)

1. Objectives of hydrometric networks

2. Design of hydrometric networks

3. Diagnostic of hydrometric networks

4. Rationalisation and optimisation of hydrometric networks

5. Application : – Diagnostic of the hydrometric network on the Volta Basin– Definition and Design of the Volta-HYCOS hydrological

network

Design and

optimisation of

hydrometric networks

1. Objectives of

hydrometric

networks

• A hydrometric

network is

aimed

at

giving

the hydrological

information to be

used

for the

following

needs

:

– Assessment of the

regional

or national surface water resources

and of their trends (climatic and

anthropogenic impacts)– Water resources planning for management and utilisation

– Estimation of environnemental, economic and social impacts of current or planned management practices on WR

– Analysis and forecasting of extreme events (warning) : drought, exceptional floods

• The

design of

a network should

answer

the

following questions :

– What hydrological variables are to be recorded ?– Where will they be recorded ?– What is the frequency of recording?– What is the duration of the recording programme? – What is the level of quality of the recorded parameters?

2. Design of

hydrometric

networks

• Definitions : – Minimum density of network:

• = 1st step in the establishment of a hydrological network• It enables us to determine the hydrological characteristics at

any point in the region• But cannot answer to specific needs of WR management and

utilisation • The stations in such networks should be monitored

continuously and their data should be of quality

– Optimal network

2. Design of

hydrometric

networks

• Definitions :– Optimal network:

Optimal networks enable a good interpolation between the stations at any point in the area covered by the network, with enough accuracy for WRs management and utilisation purposes

2. Design of

hydrometric

networks

• Types of networks : – National / regional networks – Representative or experimental basins

• From a few km2 to several km2• Measurements are carried out during one year up

to several years• All the hydro-climatic variables are measured

(Water levels, discharge, evaporation, evapotranspiration, infiltration…) in order to model the relation between rainfall and discharge

2. Design of

hydrometric

networks

• Types of stations making up a network :– Main gauges

Permanent stations and continously and correctly monitored. These are reference stations for statistical analysis

– Secondary

gaugesMaintained for a limitted number of years but sufficient in order to establish good correlation with data at main stations

– Special

gaugesBased on specific needs : irrigation, navigation, flood forecasting, dams management, …

2. Design of

hydrometric

networks

2. Design of

hydrometric

networks

WMO proposes a norm

of

hydrometric

stations density

for a minimal network :

(Guide of Hydrological Practices, 1994)

Physiographic

Units

Minimal Density

per

stationarea in km2 per

station

Costal zones 2750

Montaneaous zones 1000

Interior plains 1875

Hilly Regions 1875

Small islands 300

Polar and arid zones 20 000

Some rules and criteria

• For transboundary water balance : it is indispensable to have for each international river a gauge at the entrancy and/or the outlet of the country

• Confluence between a major and a minor tributary : it is useful to have a gauge in order to appreciate the discharge variation for the main river, downstream of the confluence

• Along a river, installation of a gauge should consider the other stations available on the river : if the difference between the flows at 2 stations is inferior to the margin of error of flow measurement, it is useless to intercalate a supplementary station

2. Design of

hydrometric

networks

• Case of dams :

– Station upstream of a dam enable to monitor the flows which enter the dam

– Station downstream of a dam enable us to estimate with precision the spilled flows (and/or turbined flow hydro-electric production)

2. Design of

hydrometric

networks

Dam of Toesse-Kanazoe (White Volta, Burkina)

• Case of dams :

– Valoriser of the information provided by stations situated on dams : reconstitution of natural flows from the water level in the dams with hydrological balance :

2. Design ofhydrometric

networks

∆V = Qentering

* ∆

Tflow

+ (P * Srandenue

) –

(Ev

* Srandenue

) –

Abstractions

•∆V : Variation of volume of dam (m3)•∆

Tcrue

:

Duration of flood (s)•P : Rainfall on the dam (mm)•Srandenue

: Surface of dam (m2)•Ev

: Evaporation on the dam (mm)•Abstractions :

Abstractions of water (AEP, irrigation, …) in the dam

Some rules and criteria :

• Rivers passing through or near a city where there’s important abstraction from the river : a station upstream and a station downstream of the city are necessary

• Region with large irrigable area with appreciable abstraction from the river : a station upstream and a station downstream of the irrigable area are necessary

2. Design of

hydrometric

networks

Water Supply pomping station at Nawuni (Ghana)

Water Supply pomping station at Nawuni (Ghana)

• To optimise a network, is to find the best compromise between the richness and the interest of hydrological

information on the

one

hand, and the cost

of

acquisition of data on the

other

hand

• Context in West Africa: important degradation of networks since the 80’s -90’s (reduction of budget of hydrological services / pullout of IRD / ex-ORSTOM in francophone countries)

• Necessity of rationalising existing networks by selecting the stations which must be monitored as priority

3. Rationalisation and

optimisation of

hydrometric

networks

• Technics of optimisation of networks (complementary)– Survey among users of data on the usefulness of each station of

the network ;– Multi-criteria analysis based on indicators which enable us to

appreciate the usefulness of each station in the network and to characterize it


1. Survey technics

– Objective :Highlight the level of utility of each station on the basis of the use of data by users

– Method : questionnaires

– The survey enables us to highlight : A) The type of use of the station :

– stations which are used for management and other decision;– station which are used for regional and long-term analysis of

water resources– station which are used for design and planning purposes


1. Survey technics

– The survey enables to highlight :

B) The use of data at the station: – Flood forecast and warning;– Current Management (navigation, level control, dam

management, monitoring of floods and drought,..)– Legal obligation (minimum discharge to be maintained)– Long term statistics (flood frequency analysis, trend

analysis, quartiles etc)– Regional hydrological Analysis (Regional regression

equation for quartiles, regional parameters of hydrological models,..)


1. Survey technics

– The survey enables to highlight :

B) The use of data at the station : – Hydraulic and hydrological design (design of reservoirs,

hydro-power infrastructure, hydraulic infrastructure,..)– Planification of water resources (planification for water

distribution, ..)– Water quality analysis (quality monitoring, quality

modelling, sea water intrution,..)– …


1. Survey technics

C) Identify the users of data at the station :– Governmental institutions (NHSs, Agriculture, Fishery, …)– Basin organisations;– Dams managers;– Consulting firms;– environmental monitoring institutes– Research institutes, Universities, – …


2. Multi-criteria analysis of network

– Objective : diagnose the stations of a network on the basis of different criteria / indicators

– Mean : Points can be attributed to each criteria in order to determine a global score for the station, which will be monitored in priority

– Criteria of evaluation of stations



Criteria

of

evaluation

of

stations :

- Regional representation of the station : - Is the station representative of a basin and/or of a climatic

zone ?– Drainage area at the station– Lengh of time of the series at the station :

- Longevity of the station (reference stations with series of data > 30 years)

- Regularity of observations of water levels (series with few gaps)

– Level of correlation between the station and other reference stations



Criteria

of

evaluation

of

stations :

- Stability of the station in time- Constructions upstream or downstream of the station can

modify conditions of flow- Beware of loss of staff gages or reference pillars (bench

marks) (eg : following to construction of bridges, …) - Quality of data at the station :

- Quality of water level data (recordings and readings)- Quality of rating curve : number flow measurements, and

stability of rating curve



Criteria

of

evaluation

of

stations :

- Usefulness of the station (on the basis of survey) :• Forecasting of High and low flows• Evaluation of flows within riparian countries ;• Evaluation of resource at national level for planification, management and

la prise of decision ;• Evaluation of change on the long term• …

- Accessibility- Economic criteria :

- Running cost (depends on type of equipement, frequency of visits, organisations of field missions)

- Cost of maintenance of the stations

GIS approach for evaluation of hydrometric networks :Example of assessment of Burkina’s national hydrometric network – SNIEau

(National System Information ), 2004

- Spatial distribution of hydrological data in the country. Spatial parameters :• Density of hydrometric of stations • Quality and continuity of data • …

«

Availability

of

hydrological

data in the

sub

basins in Burkina »

(from

SNIEau, 2004)


NonePoorLowAverageGoodExcellent

Example of assessment of Burkina’s national hydrometric network – SNIEau (National Information System on Water), 2004

- Overlapped spatial information on :

- Availability of hydrological data

- Needs for hydrological data (population density, dams projects, …)…

- … Helps to better assess the weak points of the hydrometric network and to better plan its development

GIS approach for assessment of hydrolometric networks :

« Population density

per

basin and

hydrometric

network

» (from

SNIEau, 2004)


Some data on the Volta Basin :

– Transboundary basin shared between 6 countries : • Benin• Burkina• Cote d’Ivoire• Ghana• Mali• Togo

– Superficy : 400 000 km2

– Hydrographic network : • Black Volta (‘Mouhoun’ in Burkina Faso) • White Volta (‘Nakambe’ in Burkina Faso) • Red Volta (‘Nazinon’ in Burkina Faso) • OtiAkosombo dam (constructed in1964) : volume 148 billion m3 (of which 60Billion m3 are usable)

4. Diagnostic of hydrometric network on the Volta Basin

the

Volta Basin

Logo.shpBeninBurkina FasoGhanaIvory CoastMaliTogo

Voltal.shp01234

L_volta.shpVolta delta.shpTouspays.shp

0.002 0 0.002 0.004 Miles

N

EW

S

Distribution of the Area of the Volta basin between the different counties of the basin

4%

43%

3%

40%

4% 6%BéninBurkinaCôte d'IvoireGhanaMaliTogo


Black Volta

Oti

Blac

k Vo

lta

White Volta

Red VoltaW

hite Volta

The

hydrographic

network of Volta basin

Digital Elevation Model of the Volta Basin(from G. Jung « Regional Climate Change and the impact on hydrology

in the Volta Basin » - 2006)

Area of

basin (km2)

% of

total area of

Volta basin

Mean

annual

flow

(x106

m3)

Contribution of

basin to Mean

annual

flow

Black Volta 149 000 38 % 7673 20 %White Volta 105 000 27 % 9565 25 %

Oti 73 000 19 % 11215 29 %Lower Volta 63 000 16 % 9842 26 %

TOTAL 390 000 100 % 38295 100 %

Some data on the Volta Basin :

• Flow by sub-basin :


From W. Andah, N. Van Giesen, C. Biney –« Water, Food and Climate under changing Environnemnts - Volta Basin Report »

The hydrometric network on the Volta Basin :

• Distribution of stations per countries :

CountriesArea of

Volta basin in the

country

Number

of

stations in the

Volta Basin (currently monitored)

Density

of

stationsArea/station

Density

of

stations recommended

by WMO

Benin 17 098 2 8549 17 (Mountaneous)

Burkina 178 000 55 3236 95

Cote d'Ivoire 12 500 3 ? 4167 7

Ghana 167 692 67 2503 89

Mali 15 392 0 - 8

Togo 26 700 9 ? 2967 27 (Mountaneous)

TOTAL 417 000 136 ? 3066 222


Distribution of hydrometric

stations on

the

Volta Basin

Evolution du nombre de stations hydrométriques exploitées sur le bassin de la Volta

0

10

20

30

40

50

60

70

80

90

100

110

120

130

Bénin Burkina Côte d'Ivoire Ghana Mali Togo

Nombre de stations sur le bassin de laVolta suivies historiquementNombre de stations sur le bassin de laVolta actuellement suivies

Hydrometric network on the Volta basin

• Trends in number of stations in the basin :


Hydrometric network on the Volta basin

• Trend in number of stations in the basin :


countries

Number

of

stations on the

Volta Basin (currently

monitored)

Number

of

stations on the

Volta Basin (before monitored)

Stations closed

or out of

use

Bénin 2 5 3

Burkina 55 128 73

Côte d'Ivoire 3 6 3 ?

Ghana 67 124 57

Mali 0 3 3

Togo 9 20 11

TOTAL 136 ? 286 150

Definition

and

implementaion

of

the

Volta-HYCOS network

Methodology: • Consultation of

NHSs

and

of

users

of data on the basin• Selection of stations Volta-HYCOS

on the basis of following classifcation :– Classe 1 : Stations essential at regional level (Stations

controlling cross-border flows, Stations controlling the operation of dams of regional importance, Reference stations with long periods of historic data

– Classe 2 : Stations essential at the national level (Stations for the calculation of the main water balance at the country level)

– Classe 3 : Stations of secondary importancespecific local needs (flood forecasting, Water Supply, …)


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300 0 300 600 Miles

N

EW

S

Station Volta-HYCOS

networks nationaux

0 50 100 km

Karimama

MalanvilleGuéné

KassaKandero

Banikoara

Goumon Kandi

SégbanaGogounouKérou

Porga

MatériTanguiéta

Kobli Kouarfa

Natitingou

BoukoumbéPéhonko

Sinendé

Bembéréké

Toumé

Basso

Kalalé

NikkiGuessou

SudNdali Péréré

BoriDjougou

Kopargo

Ouaké

Alédjo

Guinagourou

Parakou

Bétérou

AliafiarouTchaourou

KiliboOuèssèPim

Banté

Otala

Savé OkéOwoGlazouéSavalou

Dassa OkpaDjaloukou

Agouna

Abomey

Djidja

Bohicon

Kétou

PobéBonou

TottoLaloAplahoué

Lokossa

Comé Ouidah

Cotonou

PORTONOVO

Mék

rou

Sata

Ali b

ori

Mék

rou

Bouli

Tass

iné

Pend

jari

Ouémé

Zou

Oué

mé

Allada

LacNokoué

Okp

ara

Volta basin catchment boundary

Tele-transmitted station

Station without tele-transmission

PORGA

KORONTIERE

TIELE

Ouahigouya

Kaya

Ouagadougou

Koudougou

Bobo Dioulasso

Banfora

Kpéré

Djgoué

Gaoua

Vigué

Bondigui

Ouo

Sidéradougou

Oualokanto

OuéléniOrodara

Koloko PéniLéo

Léna

KoumbiaBanzo

Bama

Djigouéra

Faramana

Sami

Satiri

BékouiPadéma

Pa

Fara

Pô Kompienga

Parma

Madjoari

Namounou

Diapaga

Botou

Kantchari

Matiakoali

TôSili

Boromo Manga

Kayao

DjaboFada-Ngourma

Foutouri

Gayéri

Bartibougou

MansilaLiptougou

Bani

KoalaSolna

Sebba

Yamba

Bilanga

Piéla

Mani

TionBogandé

Sampelga

Tibati

Boundoré

Dori

Falagountou

Seytanga

Markoy

Tin Akof

OursiDéou

Gorom Gorom

Gorgadji

Koutougou

AribindaBaraboulé

Djibo Tongomayé

DabloPensa

Yalgo

Ban

KainSolé

Pobé MangaoTitao

Pissala

Ziga

ZogoréToéni Séguénaga

Kongoussi

Kombori

Koupéla

Zoungou

DialgayGarango

TenkodogoNiago

Koubri

ZiniaréSiglé

Bagassi

BonaKona

TchéribaDédougou

Di

Bagaré

Tikaré

Mané

Toéguen

Tougo

Oualé

Tapoa

Diamongou

Sirba

Nakambé

Volta RougeSilissi

Volta Noire

Léraba

Com

oé

Volta

Noi

re

Kossi

Béli

0 50 100 km

Dédougou Regional hydrological office

SAMANDENI

NWOKUY

PONT DE LERY

YARAN

LAHIRASSO

TENADO

BOROMO

OUESSA

DIEBOUGOU

DAPOLA

BATIE

NOUMBIEL

RAMBO

BARRAGE DE KANAZOE

LAC DE BAM

KOMPIENGA AVAL

BAGRE AVALZIOU BITTOU

DAKAYE

TAMPELGA

WAYEN

KOUNOUARLY




Tengréla

BoundialiOdienné

Touba

SéguélaMankono

Korhogo

Katiola

Ferkessédougou

Dabakala

Bonna

Bondoukou

TandaBiankouro

Danané Man

Guiglo

Duékoué

Zuénoula

BouafléDaloa

BouakéBéoumi

Sakassou

Tiébissou

Vovoua

Tabou

San Pédro

Soubré

Issio

Simbra

Gagnoa

Sassandra

YAMOUSSOUKRO

Mbahialara

Doaukura AgnibilékrouBakanda

Dimbokro

FourmaoOumé

Lakola

Diva

Bangouanou

Tiassalé

Grand Lahou

Abengourou

ABIDJAN

Dobou

Bongouanou

Agboville

Alégé

Grand Bassam

Abaisso

Adiaké

0 50 100 km

Grabo

Sassandra

Limite du bassin de la Volta

Station avec télé-transmission

Station sans télé-transmission

Bondoukou Direction régionale

TAGADI

RTE TAGADI

POUON

0 50 100 km

Hamalé Tumu Navrongo

Bolgatanga

Bawku

Garu

Nakpanduri

Wiasi

WalembeleHan

Finn

Wa

Ga

Pigu

Wawjawga

Gushiago

SaveluguSekoleg

YendiSang

Zabzugu

TamaleDaboya

Sawla

BoleDamongo

Nterso

Wangasi-Turu Bimbila

Mpaha

Kabago Salaga

Bamboi

KintampoBanda

Sampa

Wenchi

Prang

YejiChindiri

Dumbai

Kwadjokrom

Ntoaboma

Amankwakrom

Nkenkaasu

Jamasi

SunyaniWamanfo

Bechem

TepaGoaso Agogo Forifon

Kpandu

Have

Ho

Dzodze

Keta

Ade

Dawa

Tema

ACCRA

Koforidua

Nwasam

AdowsoBompata

Nkawkaw

Kumasi

Bekwai

ObuasiKibi

Kade

OdaAsamankese

Swedru

Winneba

BuakuBibiani

Awaso

Dadiaso

Jamuro

Elubo

Half Assini EsiamaAxim

Sekondi-Takoradi

TarkwaKrabo

Cap Coast

Saltpond

Manso

Foso

Dunkwa

Ayenfuri

Bawdia

Prestea

VoltaN

oire

Kulpawn

Nasia

Volta

Noire Daka Oti

Lac Volta

VoltaBi

rim

Pra

Tain

Bia Tano

Ofin

Afram

Kumasi

LAWRA

CHACHE

BUI DAM

AKOSOMBO DAMAKOSOMBO AVAL

AFRAMSO

ASUBENDEBAMBOI

DABOYANAWUNISABOBA

YAGABA

WIASI

YARUGUNANGODI

PWALAGU

Volta

Volta

Volta

Noire

Pru

Regional hydrological office




•BAÏ

•GOERE

•PLETO

Kayes

BAMAKO

Ségou

Mopti

Sikasso

KadioloKolondiébaYanfofila

KéniébaKita

Bafoulabé

YélimanéNioro

Diéma

KatiKoulikoro

Banamba

Mourdiah

Nara

Niono

Mampala

Dioila

Bougouni

Kangaba Yorosso

Koutiala

San Tominian

Djenné

Koro

Bankass

BandiagaraSévaré

DouentzaYouvarou

Niafounké

Goundam

Tombouctou

Gourma - Rharous

Bourem

Gao

AnsongoMénaka

Tidamène

Araouane

Taoudenni

Tessalit

Abeibara

KidalTi-n-Zaouâtene

Niger

Bani

Faléme

Bao

ulé

Ezgueret

0 200 400 km

Mopti

PLETO

GOERE

BAÏ





Mono

Zio

Anié

Mon

oMô

Sinkassé

Dapaong MANDOURI

Nano

Tandjouaré

Mogou

Nadoba

Kandé

PagoudaNiamtougou

Takpamba

Katchamba

Kandjo Guérin-Kouba

Kabou Bafilo

BassarDimori

Baghan

Aléhéridé

Sokodé

Balanka

Tchamba

Yanda

Kamiha

Efofami

LamaDéssi

FazaoTindjassé

Blitta

Yégué Langabou

NotséKpalimé

Tsévié

LOME

Atakpamé

Assoukoko

KoloKopé

Anié

Badou

AmiaméLomNava

Glei

Asrama Tohoun

Aného

Vogan

Noépé

KévéBatoumé

AgouGadzépé

Nyitoé

Adéta Agbatitoé

Haito

Gboto

Tabligbo

Gamé

Gapé

Sotouboua

Kpékplémé

0 40 80 km

Lac Togo

Barragede Nangbeto

Oti

Kara

Ogou

KARA

MANGO

Sérégbéné

Kara

Kéran

Koumongou KOUMONGOU

Kara

TITIRA

BONGOULOU

N'NABOUPI

KESSIBO

BORGOU

POUDA

KPESSIDE





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Volta-HYCOS stations used

for measurement

of transboundary

flows

Yaran

(Sourou

BF)

Pleto

(Sourou

MALI)

Ouessa

(Black Volta BF)

Noumbiel

(Black Volta BF)

Dapola

(Black Volta BF)

Lawra (Black Volta GH)

Tagadi

(Black Volta CI)

Bagre

(White Volta BF)

Bui

Dam (Black Volta GH)

Saboba

(Oti GH)

Mango (Oti TOGO)

Mandouri

(Oti TOGO)

Porga

(Oti BENIN)

Design and optimisation of hydrometric networks. Objectives of hydrometric networks 2. Design of hydrometric networks 3. Diagnostic of hydrometric networks 4. Rationalisation and optimisation

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