Water Simulation

XPSWMM by xpsoftwareis said to be complete software package for modeling stormwater and wastewater flows and pollutants. It may be used by scientists, engineers and resource and asset managers to simulate natural rainfall-runoff processes and the performance of engineered systems that manage our water resources.
 
xpswmm is used to develop link-node and spatially distributed models that are applied to [...]

ESRI web site includes a section named The Resource Center for Water Utilities Management:
The web site is for the ArcGIS water, wastewater, and stormwater utility community. It provides useful templates and best practice information enabling you to implement ArcGIS to manage your water utility information, perform your daily operations, and support your long term planning.

An [...]

Flow Calc is a commercial  computer software program designed to calculate common Open Channel Flow hydraulic characteristics using only the methods of the Manning’s Equation for regular and irregular channel geometries for steady uniform flow including circular and elliptical pipes.

From Flow Calc web site:
Flow Calc provides an easy to use interface that is streamlined and simplified [...]

Optimatics developed a software tool, named OptiCritical, to assist clients in analyzing and understanding the impact of pipe bursts on their water distribution systems. According to Optimatics, OptiCritical will be providing answers to questions such as:

Which pipes cause the most disruption if they break?
Which locations are affected by bursts at other locations?
Can we guarantee [...]

PCSWMM.NET, from CHI, is a spatial decision support system for US EPA SWMM 5 urban drainage modeling (sanitary, storm, combined and watershed systems).
From CHI web site:

Built from the ground up around a modern, powerful GIS engine that works seamlessly with the latest GIS data formats, PCSWMM.NET implements advanced, intelligent tools for streamlining sewer collection system [...]

MWH Soft announced the availability of the V4 Generation of InfoSewer for power ArcGIS (ESRI, Redlands, CA) users.
From MWH Soft web page:

InfoSewer is a powerful ArcGIS-based computer program for use in the planning, design, analysis, and expansion of sanitary, storm and combined sewer collection systems. The program can be effectively used to model both dry-weather [...]

From Energy-Solutions:
pipelinestudio is the industry-leading tool for design and off-line simulation of pipeline networks. It features:
* Quick and easy project setup
* Advanced hydraulic models for liquids and gas
* Steady-state and transient simulation

pipelinestudio improves the efficiency and accuracy of offline planning and design simulation through advanced offline simulation techniques for both natural gas and liquid pipelines. [...]

BOSS International released two updates:
Multiple River Reaches in RiverCAD XP

RiverCAD XP now fully supports multiple river reaches allowing you to model dendritic river networks. RiverCAD XP fully integrates with LDD and Civil3D software.
RiverCAD XP for AutoCAD is a sophisticated river modeling software that completely automates HEC-RAS and HEC-2 within AutoCAD. Its slick GUI interface [...]

MathWorks, the makers of Matlab, released a new product that models and simulate hydraulic systems – SimHydraulics.
SimHydraulics extends Simulink with tools for modeling and simulating hydraulic power and control systems. It enables you to describe multidomain systems containing connected hydraulic and mechanical components as physical networks. It provides a representative library of hydraulic components and [...]

From Wallingford Software press release:
Wallingford Software announces that the next release of its flagship wastewater network management solution, InfoWorks CS v7.5, adds a powerful new capability for those seeking to accurately model overland urban flooding. This new feature, available this summer, produces flood mapping to represent flood depths and area of spread across the [...]