---
title: "Junctions and Reservoirs | Technical Reference"
slug: "junctions-and-reservoirs"
description: "Read about junctions and reservoirs."
tags: ["1D river modelling", "1D urban modelling", "reservoir", "junction"]
updated: 2022-08-07T16:40:38Z
published: 2022-08-07T16:40:38Z
canonical: "help.floodmodeller.com/junctions-and-reservoirs"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Junctions and Reservoirs

The program is able to model looped and branched channels. For routing reaches the direction of the flow must be from upstream to downstream. The reverse is not allowed.

Rules are required to define the split of flows at bifurcations and junctions. These are defined in the [Abstraction](/v1/docs/abstration) which can be attached to the standard [Junction](/v1/docs/junction) or [Reservoir.](/v1/docs/reservoir)

A bifurcation, for example, has one inflow and two outflows. Two [Abstractions](/v1/docs/abstration) are required at the downstream nodes to define the split of flows.

In general:

Qin = Qout

If a [reservoir](/v1/docs/reservoir) is to be modelled, [abstractions](/v1/docs/abstration) must be attached to all the outflows.