Investigating the severity, continuity and frequency of climatic droughts in the east of Gilan (Samoush basin)

Dissertation for Master's Degree

Department of Natural Geography

Abstract

Iran is a vast country that has a different climate due to its special location and topographic features. For this reason, most of Iran is located in the dry climates of the world. In addition to the lack of rainfall, extreme fluctuations of rainfall in daily, seasonal and annual scales are among the characteristics that cause insufficient confidence in receiving the minimum rainfall required for agricultural purposes, feeding surface streams and underground water table, and human uses. Due to the existence of severe negative fluctuations in rainfall in different regions of the country, the occurrence of these droughts imposes a very harmful effect on the agricultural and economic sectors of the country. Drought is the result of interactions between natural and social environment. These effects are not only effective on the production of agricultural products, but simultaneously on all living organisms, including plant and animal species, as well as humans. Drought studies are of great importance in terms of natural and human aspects because the effects of drought are different in different economic and social sectors and can cause irreparable damage in different sectors. In this research, the author investigated the intensity, continuity and frequency of climatic droughts in the Samoosh basin located in the east of Gilan by using common methods such as SPI, standard index, moving average, rainfall index, normal percentage index and SPI method in order to investigate the climatic and hydrological sensitivities in the studied basin to the droughts that have occurred. 10 years of the studied statistical period have a dry state, 14 years are wet and 6 years are in a normal state, according to the normal percentage indicators, there are 9 years of drought, 6 years of mild drought, 13 years of moderate drought, one year of severe drought and one year of wet year. According to the statistical period in the Samoosh Basin, 23 years are very dry based on the indicators of the standard distribution method, 6 years are dry and one is normal and based on the indicators The SPI method in the Samoosh basin has 13 extremely dry years, 6 very dry years, 6 moderately dry years, 4 close to normal years, and one moderately wet year in 1378-79.

Key words: intensity and duration, climatic droughts, watershed, Samoush, East Gilan

Introduction

Drought is the most expensive disaster. It is natural, so that it causes an average of 6 to 8 billion dollars of damage to the world every year. The southern shores of the Caspian Sea, which includes the three important provinces of Gilan-Mazandaran-Golestan, and the pole of agriculture, animal husbandry, etc. . . is Considering the water requirement of rice cultivation is 8000 cubic meters per hectare and horticulture is 2140 cubic meters per hectare, and considering that more than 60% of the water of large and small rivers in this province is wasted, in the conditions of drought and lack of water, the agricultural and animal husbandry sectors and even industrial activities suffer severe damage, causing a serious decrease in water resources, the spread of diseases and plant pests, forest and pasture fires, and a decrease in income, followed by the migration of manpower from the village to becomes a city The greenery of the area covers many problems of water shortage and few people think that there is really a severe drought in this area. Therefore, the recognition and monitoring of droughts and their control in such areas is of particular importance (Meteorological Organization website).

According to the above, this research intends to investigate the intensity, continuity and frequency of climatic droughts in the east of Gilan (Samoush Basin) by using existing methods, therefore, we divide the current research into the following six chapters: Research

Chapter three: natural characteristics of the scope of the research

Chapter four: materials and methods.

Chapter five: research findings

Chapter six: interpretations and suggestions and answers to assumptions, sources and references.

Chapter one

general research

. Problem statement

Drought is one of the challenges of the present century, which will be considered one of the major problems of humanity in the future. Population growth, agricultural and industrial activities, and the excessive expansion of cities have led to the intensification of water resource consumption and the creation of regional crises caused by drought in many parts of the world.. The water of this yard source is considered as one of the three main factors in the formation and survival of the environment (soil, air, water) more than ever before. The importance of this issue is due to the ever-increasing need and the decrease in water quality in the world as a result of the negligence and profit seeking of individuals and organizations, which has increased day by day in such a way that it will cause acute political and social issues in the near future (Meteorological Organization website).

Our country is located in one of the arid and semi-arid regions of the world, and dryness is part of its nature and its inherent characteristic. Extreme changes in the amount of precipitation, intensity and distribution of rainfall, and temperature fluctuations are permanent characteristics of these regions. Drought also happens as a temporary complication every few years in these areas, and as a result, the damaging effects of drought in different dimensions, stagnate the development plans of the country and create widespread political, social and economic crises in different regions of the country. Due to its climatic conditions and special geographical location, Gilan province is always seen as a province without problems, while this province is full of danger from west to east. Samush basin in the east of Gilan province is one of the river basins that has been affected by this phenomenon in recent years, and it seems that the drought in this city has a climatic aspect and is caused by the lack of rain in this region. Therefore, this research intends to investigate the severity and continuity of climatic droughts in the Samoosh basin in order to make the necessary planning to prevent existing risks.

1-2. Research question

Are there climatic droughts in the Samoosh basin?

Are the climatic droughts severe and continuous in the Samoosh basin?

1-3. Objectives of the research

- Investigating the severity and continuity of climatic droughts in the Samush basin

- Knowing the type of drought at the basin level

- Providing suitable solutions to solve or deal with drought

1-4. Hypothesis

There are climatic droughts in the Samoosh basin.

Climatic droughts are intense and continuous in the Samoosh basin.

1-5. The type of research method is descriptive and analytical research method with practical goals and using library and documentary studies 1-6. The method of collecting information

The method of collecting information is library, document and field. In this research, in terms of its theoretical-practical nature and the issues raised, two methods of documentary and field study have been used. In the method of document study, methods of collecting information, data, statistics, using libraries and archives of organizations and the Internet have been used. In the field method, objective observations and interviews have been used.

1-7. Information collection tool

Information collection tool in the library method in the form of charts, tables, maps and sketches. . . and computer networks, and in the field method, maps, observations, interviews, cameras, etc. have been used. Computer networks - observation (superficial and free) of databases and questionnaires and observation.

1-8. Information analysis method

In order to analyze the severity, continuity and frequency of climatic droughts in the east of Gilan (Samoush basin), firstly, document and library data were collected, and then classified using statistical software, and finally, using computer networks and observation (surface and free) to analyze them, and finally, after final extraction and obtaining quantitative data, they were analyzed using tables and graphs. Their analysis is discussed.

1-9. Research records

Drought is a phenomenon that has attracted human attention for a long time and many researches on droughts have been done in most countries of the world and even in Iran. So that in determining the dry periods of Australia, Gibbs and Maher (Gibbs and Mahen 1967) have taken important steps by using the decile index and sorting the monthly rainfall data. Also, Palmer Jefu is the first one who investigated the drought practically and using physical and mathematical laws in a report titled Meteorological Drought, which relied on meteorological and hydrological data in his method. Ghayor and his colleagues (1376) in the study of the extent and frequency of droughts found that Iran had a severe drought in 1970-1980 and in 1973.