MEV 012: Unit 08 - Hydro-meteorology and Climate

UNIT 8: HYDROMETEOROLOGY AND CLIMATE

---

8.0 Introduction

Hydrometeorology is the study of the transfer of water and energy between the land surface and the lower atmosphere.

It combines principles of meteorology, climatology, and hydrology to understand precipitation, evaporation, evapotranspiration, soil moisture, river flow, and groundwater dynamics.
With climate change influencing hydrological processes, hydrometeorological data is essential for effective water resource planning, flood forecasting, and environmental management.

---

8.1 Objectives

After studying this unit, you will be able to:

·         Explain the structure and components of a hydrometric network.

·         Describe precipitation processes, types, and measurement methods.

·         Understand evaporation and evapotranspiration processes.

·         Estimate soil moisture content.

·         Identify river, lake, and groundwater types.

·         Understand the hydrological cycle and movement of water.

·         Assess the impact of climate change on hydrology.

---

8.2 Hydrometric Networks and Catchment Morphology

8.2.1 Important Definitions

·         Catchment: The area contributing surface runoff to a specific point.

·         Hydrometric Station: A location where hydrological and meteorological measurements are taken.

8.2.2 Components of Hydrometric/Hydrological Network Design

·         Precipitation stations

·         Streamflow gauging stations

·         Evaporation stations

·         Groundwater observation wells

8.2.3 Impact of Climate Change on Hydrology and Importance of Hydrometric Networks

·         Altered precipitation patterns and intensity.

·         Increased evapotranspiration due to higher temperatures.

·         Variability in river flows and groundwater recharge.

·         Essential role of networks in monitoring and predicting changes.

---

8.3 Precipitation

8.3.1 Occurrence of Precipitation

Formed when moist air cools and condenses into water droplets that coalesce into rain, snow, or other forms.

8.3.2 Types of Precipitation

·         Cyclonic

·         Convective

·         Orographic

8.3.3 Measurement of Precipitation

·         Rain gauges (standard, tipping bucket, weighing type)

·         Radar and satellite observations

---

8.4 Evaporation and Evapotranspiration

8.4.1 Evaporation

Process by which water changes from liquid to vapour.

8.4.1.1 Measurement of Evaporation

·         Pan evaporimeters (Class A, ISI standard)

·         Energy balance and aerodynamic methods

8.4.2 Evapotranspiration

Combined water loss from evaporation and transpiration by plants.

8.4.3 Types of Evapotranspiration

·         Potential ET

·         Actual ET

8.4.4 Factors Affecting Evapotranspiration

·         Temperature, humidity, wind speed, solar radiation, vegetation type.

8.4.5 Estimation of Evapotranspiration

·         Penman-Monteith equation

·         Blaney–Criddle method

---

8.5 Soil Moisture

8.5.1 Estimation of Soil Moisture

·         Gravimetric method

·         Neutron probe

·         Time domain reflectometry

---

8.6 River Flow

Measurement and analysis of the volume and rate of water movement in rivers.

---

8.7 Rivers, Lakes, and Groundwater

8.7.1 Rivers

8.7.1.1 Classification of Rivers

·         Perennial, intermittent, ephemeral.

8.7.2 Lakes

8.7.2.1 Classification of Lakes

·         Tectonic, volcanic, glacial, artificial.

8.7.3 Groundwater

8.7.3.1 Types of Groundwater

·         Confined, unconfined, perched.

---

8.8 Occurrence of Surface Water and Groundwater

8.8.1 Surface Water

8.8.1.1 Sources of Surface Water

·         Rivers, lakes, reservoirs, glaciers.

8.8.2 Methods of Streamflow Monitoring

·         Velocity–area method

·         Dilution techniques

·         Acoustic Doppler current profilers

8.8.3 Groundwater

8.8.3.1 Zones of Underground Water

·         Zone of aeration

·         Zone of saturation

8.8.3.2 Aquifers and Their Types

·         Confined, unconfined, leaky, perched.

8.8.3.3 Sources of Underground Water

·         Rainwater infiltration, seepage from rivers/lakes.

---

8.9 Movement of Water on the Surface and Below the Surface

8.9.1 Hydrological Cycle

Continuous circulation of water between atmosphere, land, and oceans.

8.9.2 Behavior of Rivers Due to Silt and Sediments

·         Silt deposition altering river morphology.

·         Reduction in channel capacity and flow velocity.

8.9.3 Movement of Groundwater

8.9.3.1 Darcy’s Law for Determination of Groundwater Velocity

$$

Where

8.9.3.2 Groundwater Yield

Volume of water that can be extracted sustainably from an aquifer.

---

8.10 Let Us Sum Up

Hydrometeorology integrates climatic and hydrological processes. Understanding precipitation, evaporation, soil moisture, and water movement is crucial for water management, especially under climate change. Hydrometric networks are vital for monitoring, forecasting, and sustainable resource use.

---

8.11 Keywords

·         Hydrometric Network – System for collecting hydrological data.

·         Evapotranspiration – Combined water loss from evaporation and plant transpiration.

·         Aquifer – Underground layer of water-bearing rock.

·         Hydrological Cycle – Continuous movement of water on, above, and below the Earth’s surface.

·         Darcy’s Law – Equation governing groundwater flow.

$$