It is recommended that you explicitly specify a name and namespace for the service contract, and an action for each operation to avoid using “” and to prevent interface and method names from being exposed in the service’s contract
MSDN Library – Service Contract Versioning

Where is in the WSDL?

If you browse the service WSDL you will see all over the place.  Here is a default WCF service WSDL.

<wsdl:definitions name="Service1" targetNamespace="" xmlns:wsdl="" xmlns:soap="" xmlns:soapenc="" xmlns:wsu="" xmlns:xsd="" xmlns:soap12="" xmlns:tns="" xmlns:wsa="" xmlns:wsp="" xmlns:wsap="" xmlns:wsaw="" xmlns:msc="" xmlns:wsa10="" xmlns:wsx="" xmlns:wsam="">
    <xsd:schema targetNamespace="">
      <xsd:import schemaLocation="http://localhost:63720/Service1.svc?xsd=xsd0" namespace=""/>
  <wsdl:message name="IService1_DoWork_InputMessage">
    <wsdl:part name="parameters" element="tns:DoWork"/>
  <wsdl:message name="IService1_DoWork_OutputMessage">
    <wsdl:part name="parameters" element="tns:DoWorkResponse"/>
  <wsdl:portType name="IService1">
    <wsdl:operation name="DoWork">
      <wsdl:input wsaw:Action="" message="tns:IService1_DoWork_InputMessage"/>
      <wsdl:output wsaw:Action="" message="tns:IService1_DoWork_OutputMessage"/>
  <wsdl:binding name="BasicHttpBinding_IService1" type="tns:IService1">
    <soap:binding transport=""/>
    <wsdl:operation name="DoWork">
      <soap:operation soapAction="" style="document"/>
        <soap:body use="literal"/>
        <soap:body use="literal"/>
  <wsdl:service name="Service1">
    <wsdl:port name="BasicHttpBinding_IService1" binding="tns:BasicHttpBinding_IService1">
      <soap:address location="http://localhost:63720/Service1.svc"/>

Tip: Use a constant to ensure consistency

I like to use a constant to provide a consistent namespace across my services

public class Constants
    // Ensures consistency in the namespace declarations across services
    public const string Namespace = "";

How to eliminate from WCF Services WSDL

Step 1: Declare a namespace on your service contract

The namespace can be anything.  People typically use a URI of some form but it does not have to point to an actual web page.  Often people will use a version identifier in the namsepace but there are no rules about what you should do.

// Eliminate from the contract
// If you don't want to us a constant, put the URI here
// [ServiceContract(Namespace = "")]
[ServiceContract(Namespace = Constants.Namespace)]
public interface IService1
    void DoWork();

Step 2: Declare a namespace on your service

The service namespace is added with a ServiceBehavior attribute.  Using the constant ensures that the namespace is the same for the contract and the service.

// If you don't want to us a constant, put the URI here
// [ServiceBehavior(Namespace = "")]
[ServiceBehavior(Namespace = Constants.Namespace)]
public class Service1 : IService1
    public void DoWork()

Step 3: Set the binding namespace

      <service name="EliminateTempUri.Service1">
        <!-- Use a bindingNamespace to eliminate -->
        <endpoint address=""
                  binding ="basicHttpBinding"
        <behavior name="">
          <serviceMetadata httpGetEnabled="true" />
          <serviceDebug includeExceptionDetailInFaults="false" />
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" />