Himalayan study: Effect of climate change and melting of glaciers

 Abstract

Uttarakhand state of India is highly vulnerable to climate mediated risks. The study analyses the last 35 years climatological changes and historical flash flood events in the Uttarakhand state of India. Change in land forms and loss of soil has been assessed for the years of major flash flood events by using Remote sensing images.

 

Study shows that the large amount of soil displacement from higher slopes due to flash flood impacts. Sudden rise and rapid fall of water levels, as well as the high flow velocities combined with large sediment, transports

large amount of debris at the lower reaches causing heavy amount of soil losses. Excess rainfall events are the major cause of receding glaciers and upwardly moving snowline and depleting natural resources.

 

Erratic rainfall events leading to flash floods, induces changes in water resources and causes landslides to glacial melt in the Himalayas. Increased flood events are affecting water resources and are increasing the chances of deteriorating water quality and quantity within the next few decades.

 

1.INTRODUCTION

Large-magnitude debris flows in alpine basins are widely documented in the scientific and technical literature.

Past flash floods and debris flow events have often caused high numbers of casualties [Kedarnath disaster 2013], A flash flood is defined as a flood which follows shortly (i.e. within a few hours) after a heavy or excessive rainfall event [chamoli flash flood 2021] and consequently,

 

Flash floods causes serious damages and economic losses,

Importantly, flash floods and debris flow also pose a serious risk to people, as water depths and velocities can increase within a short time. Past flash floods and debris flow have often caused high numbers of casualties;

 

Flash floods are caused by short duration, high intensity, localized rainfall events. They differ from most other fluvial floods in that the lead time for warnings is generally very limited (e.g. often much less than two hours). They usually occur on catchments draining less than 1,000 km² with response times of a few hours or less[Kedarnath flood 2013]

 

 

 

1.1 BRIEF REVIEW OF PROBLEM

 

The study analyses the last 35 years climatological changes and historical flash flood events in the Uttarakhand state of India. The climate of this relatively small state varies from tropical to alpine.

 

This wide range of climatic conditions is present mainly due to altitudinal variation but degree and direction of slope, the vegetal cover and presence of water bodies also make substantial impact on rapid and unpredictable change in micro-climate and local weather.

 

Uttarakhand state of India is highly vulnerable to climate mediated risks. These events represent an important problem in Uttrakhand hilly areas, consequently having sudden increase in water depths and flow velocities, causing serious damages and economic losses and large amount of debris is collected at the lower ends. Most of the slopes are poorly vegetated and, consequently, rainfall that is normally absorbed by vegetation can run off almost instantly. All

these characteristics make those catchments prone to flash flood formation, as demonstrated by

events that occurred in the area flood prone areas. Putting together the available meteorological and hydrological data a better insight of temporal and spatial variability of the rain storm,

 

the soil moisture conditions and flash flood can be obtained. Further, GIS tools can be a used to calculate debris in the lower catchments.

 

 

 

1.2 WHAT IS GLACIER?

A glacier is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation snow exceeds its ablation over many years, often centuries.

Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses. Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers unique is their ability to flow. Due to sheer mass, glaciers flow like very slow rivers. Some glaciers are as small as football fields, while others grow to be dozens or even hundreds of kilometers long.

(a) HOW ARE GLACIERS FORMED?

Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice. Each year, new layers of snow bury and compress the previous layers. This compression forces the snow to re-crystallize, forming grains similar in size and shape to grains of sugar. Gradually the grains grow larger and the air pockets between the grains get smaller, causing the snow to slowly compact and increase in density. After about a year, the snow turns into firn—an intermediate state between snow and glacier ice. At this point, it is about two-thirds as dense as water. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny. In very old glacier ice, crystals can reach several inches in length. For most glaciers, this process takes more than a hundred years.

 

(b) Glacier Formation

 

Glaciers form during the winter season, but persist through the summer with some melt at low altitudes . Snow is deposited in the Accumulation zone, at high altitudes. This new snow is transformed into firn, becoming increasingly dense through subsequent years. As this process continues, until no air pores remain, the glacier is “ice”. This process generally occurs at higher altitudes on a hill-slope environment. As glaciers develop, the upper layers, where new snow is deposited becomes heavy. Gravitational force pulls the upper layers downward, to lower altitudes. As snow is transferred downward, it reaches an Ablation zone, where seasonal melt and transportation of glacier ice occurs. The line delineating the Accumulation zone from the Ablation zone is the Equilibrium Line .

 

 

(1): Firn:Firn is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice.

Formation

Firn is found under the snow that accumulates at the head of a glacier. It is formed under the pressure of overlying snow by the processes of compaction, recrystallization, localized melting, and the crushing of individual snowflakes. This process is thought to take a period of about one year.

 

Depth:Firn becomes ice at a depth of about 13 m¹. At sites like this with rapid snow accumulation, the depth of a firn layer, and the load on it, increases rapidly with depth.

 

 

© Glacier accumulation

A glacier is a pile of snow and ice. In cold regions (either towards the poles or at high altitudes), more snow falls (accumulates) than melts (ablates) in the summer season. If the snowpack starts to remain over the summer months, it will gradually build up into a glacier over a period of years.

(Small valley glacier)

The key input to a glacier is precipitation. This can be “solid precipitation” (snow, hail, freezing rain) and rain¹. Further sources of accumulation can include wind-blown snow, avalanching and hoar frost. These inputs together make up the surface accumulation on a glacier.

In general, glaciers receive more mass in their upper reaches and lose more mass in their lower reaches. The part of the glacier that receives more mass by accumulation than it loses by ablation is the accumulation zone.

 

The Glacier as a System. Inputs are largely from precipitation, and also from wind-blown snow and avalanches. The glacier loses mass (ablates) mainly by the processes of calving and surface and subaqueous melt.

 

Equilibrium line altitude

Most glaciers receive more inputs and accumulation in their upper reaches, and lose more mass by ablation in their lower reaches. The Equilibrium Line Altitude (ELA) marks the area of the glacier separating the accumulation zone from the ablation zone, and were annual accumulation and ablation are equal^.

Equilibrium line altitudes in a hypothetical glacier

 

(d) SNOW: Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away.

Snow is at atmosphere:

Whether winter storms produce snow relies heavily on temperature, but not necessarily the temperature we feel here on the ground. Snow forms when the atmospheric temperature is at or below freezing (0 degrees Celsius or 32 degrees Fahrenheit) and there is a minimum amount of moisture in the air. If the ground temperature is at or below freezing, the snow will reach the ground. However, the snow can still reach the ground when the ground temperature is above freezing if the conditions are just right. In this case, snowflakes will begin to melt as they reach this higher temperature layer; the melting creates evaporative cooling which cools the air immediately around the snowflake. This cooling retards melting. As a general rule, though, snow will not form if the ground temperature is at least 5 degrees Celsius (41 degrees Fahrenheit).

 

How big can snowflakes get?

Snowflakes are accumulations of many snow crystals. Most snowflakes are less than 1.3 centimeters (0.5 inches) across. Under certain conditions, usually requiring near-freezing temperatures, light winds, and unstable atmospheric conditions, much larger and irregular flakes can form, nearing 5 centimeters (2 inches) across. No routine measure of snowflake dimensions are taken, so the exact size is not known.

2. Method and data analysis:

Uttarakhand is one of the hilly states in the Indian Himalaya. It lies in the northern part of India between the latitudes 28°43′ N and 31°27′ N and longitudes 77°34′ E and 81°02′ E,The elevation ranges from 210 to 7817 m.

 The state shares its border with China (Tibet)

in the north, Nepal in the east, inter-state boundaries with Himachal Pradesh in the west and

north-west and UP in the south.

Precipitation is received mostly in the form of monsoon rainfall from June to September. However higher reaches experience snowfall in the months of

December, January and February.

The average rainfall of the region is between 1250mm and 2000mm and of this maximum is recorded in the elevation zone of 1000 to 2000 m.

 

The study was conducted for Upalda and  areas of Garwal Hills. The past study shows that this area has received three flash flood events between 2013 to 2021. No major and minor flood event has been reported from 2011 to 2014. The climatic parameters of 35 years 1979 to 2014 was analysed. Runoff for the area was estimated by curve number method.

 

The remote sensing images of 2009 and 2014 of Upalda for resource satellite, LISS III

of spatial resolution 23.5 m, was analyzed and classified. Rainfall, temperature and humidity

data of Pauri, latitude 30° 08’ 49.62” N and longitude 78° 46’ 28.34” E, 1688 m Elevation was analysed and correlated with the debris collected Uphalda, latitude, 30° 12’ 47.22” N and longitude,78° 45’ 19.49” E, 587 m Elevation.

3. Result

The study analyses the last 35 years climatological changes and historical flash flood events in the Uttarakhand state of India. The climate of this relatively small state varies from tropical to alpine. This wide range of climatic conditions is present mainly due to altitudinal variation but degree and direction of slope, the vegetal cover and presence of water bodies also

make substantial impact on rapid and unpredictable change in micro-climate and local weather.

 

Climate Change in Himalayan Region

 

The temperature and rainfall, the two most prominent climatic factors, show large spatial variation over the region as well as from valley bottom to hilltop within the same region.

shows the total annual precipitation of Pauri for 35 years. A total increase of 06.7 % have been

reported in 35 years. Figure shows that total rainfall in 2010 was exceptionally high. The study

shows that configuration and altitudinal peculiarities of mountain ranges of the Himalaya are

responsible for the variation of climate within the mountain province itself.

Shows the analysis of daily maximum precipitation from 1979 to 2014 shows that there are three major

years of events in last 35 years 1994, 2000 and 2010 in the Pauri area of Uttrakhand. Three major flood events of flash flood have been reported in 2010.

 

shows the Variation in all climatic parameters in 2010. It is evident that maximum temperature for the duration have been reduced whereas the minimum temperature has been

increased. Nearly 95% of rainfall has been occurred from July 01 to September 30, causing higher rate of soil saturation. Low wind velocity and high humidity were the normal features for that duration.. Shows that the continuous precipitation during three months duration

in 2010 followed be higher 5 days antecedent moisture conditions for at least 5times and again with high rainfall events has caused the 3 major flash flood events in the area. The elevation difference of 1101 m has increased the flood velocity and very high rate of debris movement from the higher reaches was seen.

Debris collection and Change in Land forms:

Change in land forms and loss of soil has been assessed for the years of major flash flood

events by using Remote sensing images. Study shows that the large amount of soil displacement

from higher slopes due to flash flood impacts. Sudden rise and rapid fall of water levels due to

very high antecedent moisture conditions, as well as the high flow velocities combined with

large sediment, transports large amount of debris at the lower reaches causing heavy amount of

soil losses in the area. taken place at the lower reach after the flash flood events of 2010. TableShows the change

in land use at lower reaches. Study show that the 3 major flash flood events followed by high

runoff throughout the season has efficiently contributed to soil loss. Sediment loss has been

increased to 65% followed by increase in barren area to 402%.

4.Solution:

A sustainable flood protection policy has therefore been suggested for land-use planning maintenance of the systems and to implement structural measures,  It has been suggested that environmental concerns, flood protection and soil conservation measures, economic factors and participatory management must be included in the planning process for early benefits.

5.conclusion:

It was observed that excess rainfall events followed by high antecedent moisture conditions for more than 5 days are the major cause of flash floods in the area. Receding glaciersand upwardly moving snowline and depleting natural resources further contribute to the events. Erratic rainfall events leading to loosening of soil, induces changes in water resources, causes landslides and glacial melt in the Himalayas. Increased flood events are affecting water resources and are increasing the chances of deteriorating water quality and quantity within the next few decades. The debris flow control, flood control and flood risk management demand area specific special procedures for disaster mitigation and Management.

 

6.Acknowledgement:

I am thankful to Prof. A.C Narayana,  Center for Earth, Ocean and Atmospheric Sciences, University of Hyderabad for providing us this opportunity to do our summer internship project during this difficult time of Covid-19 pandemic.

  Chandan Jhinkwan

Centre for Earth, Ocean and Atmospheric Science 

School of Physics, University of Hyderabad

Hyderabad - 500046