GATE Overflow for GATE ESE - Recent questions in Environmental Hydraulics

GATE ES 2026 | Question: 9

Mon, 23 Feb 2026 13:15:32 +0000

Consider the following statements regarding the pressure measured at a point in a fluid.

$\text{S}1$: Absolute pressure is gauge pressure plus atmospheric pressure.
$\text{S}2$: Gauge pressure is measured by considering absolute zero pressure as datum.
$\text{S}3$: Absolute pressure is measured by considering atmospheric pressure as datum.
$\text{S}4$: Vacuum pressure is negative pressure obtained by subtracting absolute pressure from atmospheric pressure.

Which ONE of the following options lists all the TRUE statements?

$\text{S}1$ and $\text{S}2$
$\text{S}2$ and $\text{S}3$
$\text{S}1$ and $\text{S}4$
$\text{S}1, \text{S}2$, and $\text{S}4$

GATE ES 2026 | Question: 25

Mon, 23 Feb 2026 13:15:01 +0000

Water is flowing at the rate of $15 \mathrm{~m}^{3} / \mathrm{s}$ through a rectangular channel of $5$ $\mathrm{~m}$ width.

If the acceleration due to gravity $(g)$ is $9.81 \mathrm{~m} / \mathrm{s}^{2}$, the critical velocity for the flow is $\_\_\_\_$ $\mathrm{m} / \mathrm{s}$ (rounded off to three decimal places).

GATE ES 2026 | Question: 45

Mon, 23 Feb 2026 13:14:30 +0000

A cylindrical roller gate of diameter $6.0$ $\mathrm{m}$ and length $10.0$ $\mathrm{m}$ is placed on a dam to store water behind it, as shown in figure.

The magnitude of the resultant force due to water acting on that gate when the water is about to spill is $\_\_\_\_$ $\times 10^{6} \mathrm{~N}$ (rounded off to two decimal places).

Consider acceleration due to gravity $(g)=9.81 \mathrm{~m} / \mathrm{s}^{2}$; density of water $(\rho)=1000 \mathrm{~kg} / \mathrm{m}^{3}$; and $\pi=3.14$.

GATE ES 2025 | Question: 7

Thu, 06 Mar 2025 16:22:42 +0000

For a gradually varied flow, consider the following statements

$\mathrm{P}: y_{n}>y_{c}>y$ in $M_{3}$ surface profile

$\mathrm{Q}: $y_{n}<y_{c}<y$ in $S_{1}$ surface profile

where, $y_{n}$ is normal depth, $y_{c}$ is critical depth, and $y$ is flow depth.

Choose the correct option from the following

$P$ is TRUE; $Q$ is TRUE
$P$ is TRUE; $Q$ is FALSE
$P$ is FALSE; $Q$ is TRUE
$P$ is FALSE; $Q$ is FALSE

GATE ES 2025 | Question: 8

Thu, 06 Mar 2025 16:22:38 +0000

Match the following and choose the correct option from the following

$1-\mathrm{z}, 2-\mathrm{y}, 3-\mathrm{x}$
$1-\mathrm{y}, 2-\mathrm{z}, 3-\mathrm{x}$
$1-\mathrm{x}, 2-\mathrm{z}, 3-\mathrm{y}$
$1-\mathrm{x}, 2-\mathrm{y}, 3-\mathrm{z}$

GATE ES 2025 | Question: 45

Thu, 06 Mar 2025 16:21:06 +0000

A pipe line $\boldsymbol{O P} \boldsymbol{Q} \boldsymbol{R}$ branches into three pipes $\boldsymbol{X}, \boldsymbol{Y}$, and $\boldsymbol{Z}$ between points $\boldsymbol{P}$ and $\boldsymbol{Q}$ as shown in figure (not to scale)

Diameter $(d)$ and length $(l)$ of each pipe are as presented in figure and all pipes are of same material having friction factor $(f)$ of $0.02$. Assume acceleration due to gravity $(g)$ as $10.0 \mathrm{~m} / \mathrm{s}^{2}$. If the head difference between $\boldsymbol{P}$ and $Q$ is $10 \: \mathrm{m}$, then the head loss between $\boldsymbol{Q}$ and $\boldsymbol{R}$ is $\_\_\_\_\_\_ \: \mathrm{m}$. (rounded off to two decimal places)

GATE ES 2025 | Question: 46

Thu, 06 Mar 2025 16:21:04 +0000

A circular sewer pipe, having Manning's coefficient $(n)$ of $0.01$, is laid at a bed slope of $1: 100$. If it is flowing $80 \%$ full for a discharge of $2 \mathrm{~m}^{3} / \mathrm{s}$, then its diameter is $\_\_\_\_\_\_ \: \mathrm{m}$. (rounded off to three decimal places)

GATE ES 2024 | Question: 16

Mon, 19 Feb 2024 10:24:11 +0000

In the context of fluid flow, which of the following statement(s) is/are correct?

Streamline is a line, tangent to which at any point gives the direction of the velocity vector
Streakline is the actual path traversed by a given fluid particle in an unsteady flo
Streakline and streamline are same for a steady flo
Pathline and streamline are same for a steady flow

GATE ES 2024 | Question: 17

Mon, 19 Feb 2024 10:24:11 +0000

In a rectangular open channel, the flow is critical, and the flow depth is $2 \mathrm{~m}$. Select the correct statement(s)

Specific energy for the flow is $3.0 \mathrm{~m}$
Specific energy for the flow is $2.0 \mathrm{~m}$
Froude number is $1$.
Froude number is $1.5$

GATE ES 2024 | Question: 18

Mon, 19 Feb 2024 10:24:10 +0000

With respect to particle settling in wastewater treatment systems; the correct statement(s) is/are

Settling in grit chamber and primary sedimentation tanks are examples of Type-I settling
Settling in primary sedimentation tank and secondary sedimentation tank are examples of Type-II settling
Settling in grit chamber is an example of Type-I settling, whereas settling in primary sedimentation tank is an example of Type-II settling
Settling in secondary sedimentation tank is an example of Type-III settling, whereas settling in primary sedimentation tank is an example of Type-II settling

GATE ES 2024 | Question: 36

Mon, 19 Feb 2024 10:24:07 +0000

The Streeter-Phelp's oxygen sag equation for a river is based on a few assumptions. The correct assumption$\text{(s)}$ is/are

At any instant the deoxygenation rate is directly proportional to the amount of oxidizable organic material present
At any instant the deoxygenation rate is inversely proportional to the amount of oxidizable organic material present
The reoxygenation rate is directly proportional to the dissolved oxygen deficit
The reoxygenation rate and deoxygenation rate are directly proportional to the saturation concentration of dissolved oxygen.

GATE ES 2024 | Question: 37

Mon, 19 Feb 2024 10:24:07 +0000

Water is flowing FULL through a rectangular tunnel of size $3 \mathrm{~m}$ (width) $\times 2 \mathrm{~m}$ (height). The average velocity of flow is $1 \mathrm{~m} / \mathrm{s}$. The frictional head loss is observed to be $1 \mathrm{~m}$ per $\mathrm{km}$. Consider acceleration due to gravity $(\mathrm{g})$ as $10 \mathrm{~m} / \mathrm{s}^{2}$. The correct statement(s) is/are

Hydraulic radius is $0.6 \mathrm{~m}$
Darcy-Weisbach friction factor is $0.04$
Hydraulic radius is $2 \mathrm{~m}$
Darcy-Weisbach friction factor is $0.024$

GATE ES 2024 | Question: 46

Mon, 19 Feb 2024 10:24:06 +0000

With reference to the gate shown in the figure, the gate will start opening automatically when the water level ' $h$ ' above the hinge is __________ $\mathrm{m}$ $\text{(rounded off to 2 decimal places)}$

GATE ES 2024 | Question: 47

Mon, 19 Feb 2024 10:24:06 +0000

In a cyclone separator of radius $25 \mathrm{~cm}$, a particle is travelling with a gas stream at velocity of $18 \mathrm{~m} / \mathrm{s}$. The ratio of centrifugal force to the gravitational force acting on the particle is __________ $\text{(rounded off to 2 decimal places)}$.

Consider acceleration due to gravity (g) as $9.8 \mathrm{~m} / \mathrm{s}^{2}$.

GATE ES 2023 | Question: 19

Tue, 23 May 2023 03:12:24 +0000

The kinematic viscosity of glycerin and kerosene are $1.2$ times and $0.95$ times of that of water, respectively. Glycerin and kerosene flow through two identical porous media having same hydraulic gradient. Assuming Darcy's law is valid for the porous media, the ratio of flow rate of kerosene to that of glycerin is

$1.052$
$1.140$
$0.792$
$1.263$

GATE ES 2023 | Question: 21

Tue, 23 May 2023 03:12:22 +0000

The critical depth in a $2 \mathrm{~m}$ wide rectangular channel carrying a discharge of $10 \mathrm{~m}^{3} / \mathrm{s}$ and taking value of acceleration due to gravity $(g)$ as $9.81 \mathrm{~m} / \mathrm{s}^{2}$ is _________ (in m, rounded off to two decimal places).

GATE ES 2023 | Question: 25

Tue, 23 May 2023 03:12:19 +0000

River water containing two types of spherical suspended particles $\text{(clay particles, metal particles)}$ is retained in a sedimentation tank. The clay particles having diameter of $75 \mu \mathrm{m}$ and specific gravity of $2.65$ is settling in the tank with a constant velocity. The velocity of clay particles is $2$ times of that of metal particles having specific gravity of $8$. Assume discrete settling and laminar flow conditions within the sedimentation tank. The estimated diameter of the metal particles is ___________ (in $\mu \mathrm{m}$, $\text{rounded off to integer)}$

GATE ES 2023 | Question: 42

Tue, 23 May 2023 03:11:57 +0000

A trapezoidal canal lined with cement concrete $(n=0.01)$ is designed to carry a discharge of $20 \mathrm{~m}^{3} / \mathrm{s}$ at a bed slope 1 in 400 . If the bed width is twice of the depth of flow and side slope of the canal section is 2 (1 vertical:2 horizontal) then the corresponding depth of flow will be ____________ $\text{(in m, rounded off to two decimal places).}$

GATE ES 2021 | Question: 5

Tue, 14 Mar 2023 03:44:44 +0000

In fluid statics, the line of action of the buoyant force always acts through the ___________.

centre of gravity of any submerged body
centroid of the volume of any floating body
centroid of the displaced volume of fluid by the body
centroid of the volume of fluid vertically above the body

GATE ES 2021 | Question: 9

Tue, 14 Mar 2023 03:44:37 +0000

Which of the following causes $\text{'Type-I'}$ settling in a sedimentation tank?

Agglomeration
Compression
Force of gravity
Charge neutralization

GATE ES 2021 | Question: 25

Tue, 14 Mar 2023 03:44:25 +0000

A water jet discharging from a $4 \mathrm{~cm}$ diameter orifice has a diameter of 3.5 $\mathrm{cm}$ at its vena contracta. The coefficient of velocity is defined as the ratio of the actual velocity of the jet at vena contracta to the theoretical velocity of the jet. If the coefficient of velocity is $0.98$, the coefficient of discharge for the orifice will be $\text{(rounded off to two decimal places)}$.

GATE ES 2021 | Question: 44

Tue, 14 Mar 2023 03:43:56 +0000

In open channel flow, the specific energy is the total energy per unit weight of a liquid, where the component potential energy is measured from the bed of the channel as the datum.

A rectangular channel of $10 \mathrm{~m}$ width carries $20 \mathrm{~m}^3 / \mathrm{s}$ of water. The depth of flowing water is $1 \mathrm{~m}$. The specific energy for this flow condition is $\mathrm{m}$ $\text{(rounded off to one decimal place)}$.

Consider acceleration due to gravity $(g)=10 \mathrm{~m} / \mathrm{s}^2$.

GATE ES 2021 | Question: 45

Tue, 14 Mar 2023 03:43:56 +0000

Two reservoirs are connected by a pipeline consisting of two pipes '$\text{A}$ ' and '$\text{B}$ ' in series. The two pipes are of same length and have the same Darcy friction factor. If the internal diameter of pipe '$\text{B}$ ' is twice as large as the internal diameter of plpe '$\text{A}$ ', the ratio of the head loss in pipe ' $\text{A}$ ' to that in pipe '$\text{B}$ ' is __________ $\text{(answer in integer)}$. Neglect all minor losses.

GATE ES 2021 | Question: 49

Tue, 14 Mar 2023 03:43:53 +0000

A $900 \mathrm{~mm}$ internal diameter sewer is laid at a slope of $0.004$ and has an actual flow of $0.15 \mathrm{~m}^3 / \mathrm{s}$. Assuming Manning's roughness coefficient to be $0.013$, the ratio of the actual flow to the flow when the sewer is running full is__________. $\text{(rounded off to two decimal places)}$.

Take $\pi=3.14$.

GATE ES 2021 | Question: 50

Tue, 14 Mar 2023 03:43:52 +0000

A $10$ million litres per day $\text{(MLD)}$ sewage treatment plant $\text{(STP)}$ is based on the Activated Sludge Process $\text{(ASP)}$. First, the sewage undergoes primary treatment and the resulting treated sewage has $\text{BOD5}$ of $140 \mathrm{mg} / \mathrm{L}$ concentration. This is further passed through a $1500 \mathrm{~m}^{3}$ capacity aeration tank $\text{(in ASP)}$, where the mixed liquor volatile suspended solids $\text{(MLVSS)}$ concentration is maintained at $3000 \mathrm{mg} / \mathrm{L}$. The concentration of $\text{BOD 5}$ of the treated sewage is $5 \mathrm{mg} / \mathrm{L}$.
The Food to Microorganisms ratio $\text{(F/M)}$ of the $\text{ASP}$ is___________ day $^{-1}$ $\text{(rounded off to two decimal places)}$.

GATE ES 2022 | Question: 10

Fri, 17 Feb 2023 07:06:10 +0000

Centrifugal pumps with suction pipe (shown by solid arrow) and delivery pipe (shown by dotted arrow) are shown in the figures. Choose the option that gives the correct connection

GATE ES 2022 | Question: 48

Fri, 17 Feb 2023 07:05:37 +0000

A venturimeter along with a differential manometer was installed to measure flow in a water pipeline as shown in the following figure (not drawn to scale).

Taking specific weight of water as $9810 \mathrm{~N} / \mathrm{m}^{3}$, the pressure difference (in Pa, rounded off to one decimal place) between point $\mathrm{Q}$ and $\mathrm{P}$ is ________

GATE ES 2022 | Question: 49

Fri, 17 Feb 2023 07:05:37 +0000

Two reservoirs having a difference of $10 \mathrm{~m}$ in their water surface elevations are connected by a pipeline (diameter $=10 \mathrm{~cm}$, length $=50 \mathrm{~m}$, and friction factor $f=0.02$ ). If the last $25 \mathrm{~m}$ length of the pipeline is replaced by a same material pipe of diameter $20 \mathrm{~cm}$ then neglecting minor losses the discharge (in \%, rounded off to one decimal place) will increase by____________

GATE ES 2022 | Question: 50

Fri, 17 Feb 2023 07:05:36 +0000

The depth of flow (in m, rounded off to two decimal places) in a hydraulically efficient rectangular channel $(n=1 / 80)$ to carry a discharge of $64 \mathrm{~m}^{3} / \mathrm{s}$ at bed slope $0.01$ is ___________.

GATE ES 2022 | Question: 51

Fri, 17 Feb 2023 07:05:35 +0000

Clean water is passed through a bed of uniform spherical sand at a filtration velocity of $0.002 \mathrm{~m} / \mathrm{sec}$. The sand grains are $0.4 \mathrm{~mm}$ in diameter and have a specific gravity of 2.65. Bed depth is $0.67 \mathrm{~m}$ and porosity $(\eta)$ is $0.35$. Given, water density $=998.2 \mathrm{~kg} / \mathrm{m}^{3}$; water dynamic viscosity $=1.002 \times 10^{-3}$ Pa.s. Friction factor $(f)$ is given as: $f=1.75+\{150 \times(1-\eta) /(\operatorname{Re})\}$ where Re is Reynolds number. The headloss (in $\mathrm{m}$, rounded off to three decimal places) calculated using the Carmen-Kozney equation is _____________.