高等水文学第三讲

田富强

2012.09.19《高等水文学》第三讲水文过程及其观测

Hydrological

Processes

&Its

Observation2.1全球水文循环全球水文循环主要特征Coupling

and

feedbacks:

Ocean‐atmosphere‐landinteraction

—

single

coupled

earth

systemPrincipal

players:

Hadley

circulation,

thermohalinecirculations,terrestrialvegetationdistributionandsoilmoisture,snow/ice

albedoOscillations

and

variability:

decadal,

inter-annual,

intra-annual,

seasonal,sub-seasonal,dailyCharacteristics

at

different

space

and

time

scales:

largescales

feed

the

small

scale,

and

small

scales

feed

thelargescalesGlobal

water

cycle:

moisture

movement

in

all

its

phases

asadriver

andresponseoftheaboveelements大气：Hadley

CirculationThe

Hadley

cell

carries

heat

and

moisture

from

thetropics

to

the

northern

and

southern

mid-latitudes.Hadley

cellThe

Hadley

cell,

named

after

GeorgeHadley,

is

a

circulation

pattern

thatdominates

the

tropical

atmosphere,

withrising

motion

near

the

equator,

polewardflow

10–15

kilometers

above

the

surface,descending

motion

in

the

subtropics,

andequatorward

flow

near

the

surface.

Thiscirculation

is

intimately

related

to

thetrade

winds,

tropical

rainbelts,

subtropicaldeserts

and

the

jet

streams.海洋：Thermohaline

CirculationThis

collection

of

currents

is

responsible

for

the

large-scaleexchangeofwatermasses

intheocean,includingprovidingoxygentothedeep

ocean.Theentirecirculation

patterntakes~2000

yearsThermohaline

CirculationThe

term

thermohaline

circulation

(THC)

refers

toa

part

of

the

large-scale

ocean

circulation

that

isdriven

by

global

density

gradients

created

bysurface

heat

and

freshwater

fluxes.

The

adjectivethermohaline

derives

from

thermo-

referring

totemperature

and

-haline

referring

to

salt

content,factors

which

together

determine

the

density

ofsea

water.

Wind-driven

surface

currents

(such

asthe

Gulf

Stream)

head

polewards

from

theequatorial

Atlantic

Ocean,

cooling

all

the

whileand

eventually

sinking

at

high

latitudes

(formingNorth

Atlantic

Deep

Water).

This

dense

water

thenflows

into

the

ocean

basins.多

要

素

的

耦

合El

Niño/La

Niña-Southern

Oscillation,

or

ENSO,

is

aquasi-periodic

climate

pattern

that

occurs

across

thetropical

Pacific

Ocean

on

average

every

five

years,

butover

a

period

which

varies

from

three

to

seven

years.

It

ischaracterized

by

variations

in

the

temperature

of

thesurface

of

the

tropical

eastern

Pacific

Ocean

-

warming

orcooling

known

as

El

Niño

and

La

Niña

respectively-

andair

surface

pressure

in

the

tropical

western

Pacific

-

theSouthern

Oscillation.

The

two

variations

are

coupled:

thewarm

oceanic

phase,

El

Niño,

panies

high

air

surfacepressure

in

the

west

Pacific,

while

the

cold

phase,

La

Niña,panies

low

air

surface

pressurein

the

west

Pacific.Mechanisms

that

cause

the

oscillation

remain

understudy变异性年际尺度为例泰国洪水（2011.10）变异性气候变暖的影响耦合与反馈Feedback蓝圈：正反馈红圈：负反馈实线：增强

虚线：减弱Stomatalresistance2.2流域和山坡水文过程流域水文过程山坡水文过程Figure

fromSidle

et

al.,

2001

HP实际山坡照片Maimai试验流域（新西兰,2009年，1570mm/y）密云水库流域（2012.07.20,

492mm/y）巴音布鲁克草原（2012.09.17,

276mm/y）2.3主要水文过程计算及观测主要水文过程蒸发蒸腾地下水运动土壤水运动降水入渗蒸散水文过程地表径流汇流水文过程－降水降水是水分从 大气输送到地 球表面的主要 途径。降水通常包括 降雨、雪、冰 雹、雨加雪等 形式。TRMM

(The

Tropical

RainfallMeasuring

Mission

) Precipitation

Radar

(PR):

designed

toprovide

three-dimensional

maps

of

stormstructure.TRMM

Microwave

Imager

(TMI):

passivemicrowave

sensor

designed

to

providequantitative

rainfall

information

over

awide

swath

under

the

TRMM

satellite. Visible

and

Infrared

Scanner

(VIRS):

oneof

the

three

instruments

in

the

rain-measuring

package

and

serves

as

a

veryindirect

indicator

of

rainfall. Clouds

and

the

Earth's

Radiant

EnergySystem

(CERES): measures

the

energy

atthe

top

of

the

atmosphere,

as

well

asestimates

energy

levels

within

theatmosphere

and

at

the

Earth's

surface. Lightning

Imaging

Sensor

(LIS):

detectsand

locates

lightning

over

the

tropicalregion

of

the

globe.水文过程－植被截留植被截留是林冠在短时间内截持并 释放出雨水的现象。植被的截留类似于土壤的渗透现象，降雨进入林冠后产生初始截留强度，林冠饱和后，仍有一定截留能力－稳定截留强度，可用Horton入渗理论描述：水文过程－蒸发水分通过蒸发从地表向大气输送，在 此过程中水分由液态变为气态。约有80％的蒸发来自于海洋，20％来 自于内陆水体和植被。发生在土壤表 面的蒸发称为土面蒸发，发生在植物 叶面的称为植物蒸腾。风将水汽输送至全球，并影响着世界 各地的空气湿度。水面蒸发水

面

蒸

发水文过程－蒸发土壤辐射、气温、湿度和风速等气象因素土壤中含水率大小和分布E大气蒸发能力E0土壤供水能力土

面

蒸

发土面蒸发表土蒸发强度保持稳定的阶段：表土蒸发强度随含水率变化的阶段：水汽扩散阶段：田间腾发量的估算1.

理论方法紊流扩散法能量平衡法Bowen比风速 水汽压田间腾发量的估算综合法（Penman公式）干燥力田间腾发量的估算－经验方法,空气湿度：如,,水面蒸发：利用单一气象因素估算腾发量：太阳辐射：太阳辐射气温:如平均气温积温水汽压空气饱和差水面蒸发强度田间腾发量的估算－经验方法与多个气象因素复相关的经验公式：如Dalton空气动力学类型的公式，一般形式为：其中f(u)为某一适宜高度处风速u的经验函数Christiansen与Hargreaves（1969）公式：以太阳总辐射为指标，综合考虑了气温、风速、相对湿度、日照百分数和高程等因素的的影响。蒸发器直径＝61.8

cm水圈直径＝161.8

cm一般每日8时观测一次，则得到逐日蒸发的水深（mm）。蒸发皿蒸发量的折算问题E

w

'

q

'涡度相关法（Eddycorrelation

method）蒸发量可以通过测量垂直方向上风速的脉动量和水汽浓度的脉动量，并计算一定时间长度内两个脉动量的互相关得到。尽管这种方法在理论上很严密，但实际观测对仪器的要求非常严格。例如，当在距离地表几米处测量时，响应幅频应至少达到5～10Hz，即每秒测量5～10次。直到1990年代才实现仪器的商业使用，但仪器仍然非常昂贵而且使用要求很高，目前还仅限于在实验观测。清华大学位山生态水文试验基地水文过程－地表水运动1. 一维洪水运动波－圣维南（St.Venant）方程组A－过水断面面积；Q－流量；y－水深；i0－河底比降if－摩擦比降V－断面平均流速水文过程－地表水运动平面二维非恒定流动的基本方程：连续方程：动量守恒方程：x方向：y方向：水文过程－入渗水文过程－入渗降雨的入渗过 程可分为两个 阶段供水控制（通 量控制）阶段土壤入渗能力 控制（剖面控 制）阶段水文过程－入渗边界的简化入渗边界有三种简化模型：地表含水率已知——灌溉模型地表通量已知——降水模型地表积水——积水模型水文过程－入渗对于均质土壤，初始含水率分布均匀时， 可用解析或半解析的方法求解前二种情况 下的土壤水分运动方程。对于初始含水率不均匀，或土壤非均质， 或地下水埋藏较浅以及实际问题必须按较 复杂的二维或三维问题处理时，目前还只 能用数值解法。用解析方法求解时，主要困难在于该微分 方程的非线性，在求解时一般采用线性化 方法将其近似为线性偏微分方程。常用入渗公式4.

Holtan公式：饱和含水率Green-Ampt公式：稳渗率Philip公式：吸渗率 稳渗率Horton公式：稳渗率土壤初始入渗率容许储水量Green-Ampt模型Green-Ampt模型又 称活塞模型，模型 研究的是初始干燥 的土壤在薄层积水 时的入渗问题。基本假定：入渗时 存在明确的水平湿 润锋面，将湿润和 未湿润的区域截然 分开。Green-Ampt模型1.

由达西定律可求得地表处入渗率：2.

由水量平衡原理求得入渗量联立以上两式，并代入边界条件，可求3.

由得：水文过程－土壤水运动非饱和土壤水流动的达西定律：通量 水力传导度 土水势非饱和土壤水流动与饱和土壤水流动的区别：非饱和饱和土水势主要考虑重力势和基质势主要考虑重力势和压力势导水率是含水率的函数饱和导水率非饱和土壤水运动的基本方程质量守恒运动方程连续方程达西定律非饱和土壤水运动的基本

方程或

z

y

z

t

x

x

y

zx

y

K

K

K

水文过程－地下水运动渗流基本定律－达西定律适用范围：Re不超过1～10；水力坡度大于起始水力坡度J0；多数情况下粗砂中的地下水运动是符合达西定律的。非线性运动方程（Re>1~10)常用的是P.Forchheimer公式：或水文过程－地下水运动1.

渗流的连续性方程：2.

假设地下水为不可压缩液体，密度为常数，含水层骨架不可压缩，则方程可简化为：水文过程－流域汇流坡面汇流与河网汇流各有不同特点：流态不同；蒸发和下渗的影响不同；汇流速度不同；调蓄作用大小不同；坦化程度强弱；非线性程度的差别。汇流分析模型：分散型模型：对坡面流采用流速公式代替动力方程的运动波模型，以Woolhiser-Ligget的无因次化方法为代表（1967）集总式模型：用水文学方法以蓄泄关系代替动力方程，以

Horton-Izzard法等为代表（1938～1944）水文过程－流域汇流常用流域汇流计算方法：单位线法；瞬时单位线法；综合单位线法；等流时线法；单元汇流法；河道汇流常用马斯京根法。2.4地表产流机制:超渗产流和蓄满产流Infiltration

Excess

Runoff

（Hortonian

Runoff)Saturation

Excess

Runoff

(Dunne

Runoff)Hortonian

overland

flowRobert

Elmer

Horton

(1933)

at

the

age

of

58

laidthe

foundation

of

what

is

now

called

the“Hortonian

overland

flow”Soil

acts

like

a

sieve

separating

rainfall

into “infiltration”

and

“runoff”

or

“overland flow”He

believed

that

excess

of

rainfall

intensity

overinfiltration

capacity

is

the

only

source

of

runoffquick

enough

to

produce

streamflow

hydrographpeak

and

all

infiltration

posses

into

groundwaterand

constitute

the

sole

source

of

baseflow.This

idea

fitted

very

well

with

Sherman’s

(1932)“unit

hydrograph”

theory

of

basin

runoff.Horton’s

overland

flow

from

rainfall

excess

eEssential

elements

ofHorton’soverland

flow

theoryRainfall

in

excess

of

infiltration

capacity e

runoffInfiltration

capacity

decreases

with

rainfall

due

to

change

insurface

moisture,

rain-drop

packing

of

surface

particles,entrapment

of

air,

closing

of

sun

cracks,

swelling

and

washing

offine

particles.Overland

flow

will

occur

more-or-less

simultaneously

over

theentire

watershed

if

rainfall

intensity

is

greater

than

lower

limitinginfiltration

capacity

(assume

uniform

over

the

watershed)The

hydraulic

of

the

overland

flow

plays

an

important

role

inerosion.

At

some

distance

downslope

of

the

watershed

divide,

thedepth

of

the

sheet

of

overland

flow

is

sufficient

to

generate

a

shearstress

competent

to

entrain

the

surface

soil

particles.

Erosionoccurs

firstly

in

the

form

of

rills

which

can

subsequently

coalesceto

form

new

stream

channels.c

0

cwherefc

is

final

infiltration

rate,f0

is

initial

infiltration

ratef)e

kt

f

(

f

fHorton’s

Infiltration

EquationConsequence

of

the

above

theorySoil

surface

provides

a

sharp

division

of

bothhydrologic

and

geomorphic

processes,

withinfiltrating

water

contributing

only

to

longer-termsoil-

and

ground-water

recharge

and

to

baseflow,and

being

irrelevant

both

as

far

as

the

stormhydrograph

peak

and

surface

erosion

areconcerned.Notice

that

although

the

unit

hydrograph

andHorton

overland

flow

models

tied

in

extremelywell

together,

they

are

fundamentally

different.The

unit

hydrograph

a

“Black

box”

modelwhere

as

Horton’s

theory

is

based

oninvestigation

of

physical

processes

and

theirinter-relationships.Problem

with this

theoryKirkby

(1969):

Hortonian

overland

flow

willoccurinstantaneously

over

a

basin

only

if

it

is

small

and

hashomogeneous

soil,

soil

moisture,

interception,

anddepression

storage

and

infiltration

condition.Some

surface

runoff

can

exist

for

a

time

as

subsurfaceflow

which

has

been

returned

to

thesurfaceKirkby

&

Charley

(1967):

where

there

isappreciablesoil

and

vegetation,

especially

where

there

is

humus

orlitter

covers,little

overland

flow

may

be

expected

tooccur

over

much

of

the

drainage

basin,

except

in

mostextreme

storms.Many

storms

may

be

expected

to

produce

overlandflow

from

limited

contribution

area

at

much

lowerrainfallintensities

than

are

required

to

exceed

theinfiltration

capacities

over

the

whole

basin

and

so

toproduce

universal

Hortonian

overland

flow

theselimited

areas

area:Zone

at

the

slope

base,

immediate

marginal

to

stream

channelswhere,

despite

the

usually

thicker

soil,

lateral

soil

drainagecommonly

produces

high

antecedent

moisture

conditions

in

theupper

layers.

The

extent

of

such

contributing

areas

is

initiallycontrolled

by

the

soil

characteristics

and

antecedent

moistureconditions,

but

as

the

storm

continues

the

zone

of

saturation

mayextend

upslope

to

an

extent

determined

by

the

temporal

pattern

ofstorm

intensity

and

the

characteristics

of

the

slope

soil

profile,including

hydraulic

efficiency

and

available

soil-moisture

storage.Concavities

or

topographic

hollow

where

surface

flowlinesconverge.

Stream-head

hollows

are

for

this

reason

especiallysusceptible

to

surface

runoff.Areas

of

thin

soil

coverSaturation

overland

flowThe

above

have

lead

to

the

concept

ofsaturation

overland

flow

which

occurswhere

the

soil

is

saturated

(partly

bylateral

flow

in

the

soil)

even

though

thelocal

infiltration

capacity

has

not

beenexceed

by

the

rainfall

intensities.

Suchoverland

flow

is

non-Hortonian.Saturation

overland

flow

may,

undercertain

circumstance

of

rainfall

intensityand

contribute

areas,

dominate

the

stormrunoff

of

catchment.Variable

Source

AreaKirkby,

1978.

Hillslope

Hydrology产流机制的统一性分析各种径流成分(超渗地面径流、饱和地面径流、地下径流、壤中水径流)的产流机制可知，任何一种径流成分都是在两种不同透水性物质的界面上产生的，而且上层介质的透水性必须好于下层介质的透水性。从这个意义上说，任何径流量都是由“超渗”作用形成的。对任一界面以上的微分厚度土层均可写出下列形式的水量平衡方程式：芮孝芳,2004.水文学原理I

E

We

W0

F

R产流机制的统一性I

—通过界面以上介质到达界面的供水量，当界面为地面时为降水E

—通过界面的蒸散发量F

—通过界面进入下层介质的入渗量(We-W0)—界面以上介质含水量在时段内的变化，当界面为地面时，该项为0R

——积聚在界面上的自由重力水芮孝芳,2004.水文学原理主导产流类型的影响因素Dunne,

1978.

in

Hillslope

Hydrology,

edit

by

KirkbyDunne论

产

流组合产流的类型和基本产流模式sint1.R

型

超渗地面径流型（2.

Rs

Rint)型

超渗地面径流和壤中水径流组合型（3.

Rsat

Rint)型

饱和地面径流和壤中水径流组合型（4.

Rs

R

g

)型

超渗地面径流和地下水径流组合型5.(

Rint

+R

g

)型

壤中水径流和地下水径流组合型6.R

型

壤中水径流型g7.(Rs

Rint+R

g

)型

超渗地面径流、壤中水径流和地下水径流组合型（8.

Rsat

Rint

+R

g

)型

饱和地面径流、壤中水径流和地下水径流组合型9.R

型

地下水径流型来源：芮孝芳,2004,

水文学原理,P1522.5多源观测数据RadarGaugeLABZMultiple

Sources

for

Rainfall

ObservationsGeosynchronous

SatellitesVIS,

IR,

SoundingPolarOrbiting

SatellitesMV,

and

Space

RadarPrecipitation

is

among

the

single

most

important

hydro-meteo-climatic

variable;Precipitation

measurement

is

one

of

the

KEY

hydrologic

challenges, particularly

in

high

latitude,

ocean,

or

remoteregions.How

to

obtain

Precipitation

Information,

Globally?“Satellite

Remote

Sensing

is

not

an

Option

but

the

only

option

to